Methods, systems, and apparatus to synchronize actions of audio source monitors

Systems, methods, articles of manufacture and apparatus are disclosed to align actions of audio source monitors. An example method disclosed herein includes invoking an audience monitor to transmit a radio frequency (RF) initialization packet to a base unit, receiving an indication that the base unit has received the RF initialization packet at a first time, and invoking the base unit to transmit an RF acknowledgement packet to the audience monitor. The example method also includes receiving an indication that the RF acknowledgement packet is received by the audience monitor and waiting for an end to a delay period having a first value, identifying whether the audience monitor has finished processing the RF acknowledgement packet when the delay period ends at a second time, and incrementing the delay period to a second value when the audience monitor is still processing the RF acknowledgement packet and the delay period has ended.

FIELD OF THE DISCLOSURE

This disclosure relates generally to market research and, more particularly, to methods, systems, and apparatus to synchronize actions of audio source monitors.

BACKGROUND

Audience measurement activities occur in consumer households, shopping areas (e.g., stores, malls, etc.), and other areas where people may be exposed to advertisements and/or other media. To identify when a consumer was exposed to media content, what the media content contains and/or where the exposure to the media occurred, the consumer may be equipped with a mobile unit to record portions of the media content exposed to the consumer.

In some examples, the consumer is equipped with a mobile unit to record audio that may be present in an area to be monitored. Presented or rendered media, such as an advertisement or a kiosk feature presentation (e.g., at a library, a museum, an amusement park, etc.) may be presented in proximity to a base unit that can also collect audio information (e.g., a portion of presented media content). When both the mobile unit and the base unit collect audio information, one or more post-processing activities may be employed to match the collected mobile unit audio information with the collected base unit information, thereby allowing identification of consumer location and/or the type of media content to which the consumer was exposed.

DETAILED DESCRIPTION

Although the following discloses example methods, systems, apparatus and articles of manufacture including, among other components, software executed on hardware, it should be noted that such methods, systems, apparatus and articles of manufacture are merely illustrative and should not be considered as limiting. For example, it is contemplated that any or all of these hardware and software components could be embodied exclusively in hardware, exclusively in software, exclusively in firmware, or in any combination of hardware, software, and/or firmware. Accordingly, while the following describes example methods, systems, apparatus and articles of manufacture, such examples are provided are not the only way to implement the methods and apparatus described herein.

The example methods, systems, apparatus and articles of manufacture described herein may be used to analyze the movements of audience members in the course of their exposure to media sources or media presentations to aid in determining whether such media presentations were actually consumed (e.g., viewed, listened to, etc.) by the audience members. In some example implementations, the audience members may be panelist members that are statistically selected to participate in a market research study. However, in other example implementations, the audience members need not be panelist members. While mere proximity to media sources reflects an audience member's exposure, determining whether the audience member was paying attention to, consumed, and/or was engaged with such media sources requires more than proximity. For example, knowledge of an audience member's location being 5-feet from a media source (e.g., television) at one moment in time indicates exposure. However, such an audience member detected 5-feet from the media source for several moments in time (e.g., over a span of 30 minutes) indicates that the audience member may be consuming (e.g., engaged-with, paying attention to, etc.) the media presentation. Accordingly, location determination allows valuable audience member data to be collected so that media exposure and/or consumption behavior may be determined.

In particular, the example methods, systems, apparatus and articles of manufacture described herein may be implemented using, for example, tags worn or carried by audience members, and may be used to collect audience member movement information and/or media exposure information. Additionally, the movement and/or exposure information may be detected relative to media sources (e.g., a set-top box, television, stereo, an in-store display, an amusement park kiosk, a billboard, etc.) and used to determine the behavior of an audience member to thereby enable an inference as to whether the audience member is consuming media presentations. In this manner, media presentations (e.g., audio, video, still images, Internet information, computer information, billboards, etc.) may be given appropriate media consumption credit.

The example methods, systems, apparatus and articles of manufacture described herein may also be used to align an action in time between a base unit and a mobile unit. As described above, tags (e.g., bracelets, pendants or other items capable of collecting audience member information) may be worn or carried by audience members. These tags may communicate with one or more base units in an area to be monitored. The tags operate on battery power and, thus, require periodic recharging and/or replacement. As processing power of the tag circuitry increases, the amount of available field operation time decreases due to increased electrical energy requirements.

In some circumstances, a tag and a base unit attempt to begin capturing information (or other action) in an area at the same time. To ensure that a measurement of time between the tag and the base unit are synchronized, some tags employ a Real Time Clock (RTC) device, such as RTCs manufactured by Texas Instruments®, Maxim®, Intersil®, etc. However, the RTC consumes additional energy from the battery and consumes circuit board real estate that causes the tag to be larger. In other examples, the RTC causes problems related to granularity and accuracy because, in part, the RTC drifts approximately one to two seconds per day in a random manner. Over the course of months of tag operation in the field, such drift causes substantial difficulty when matching audio information between tags and base units. However, the example methods, systems, apparatus and article of manufacture described herein synchronize actions between the tag and base unit in a manner that does not require an RTC device.

Turning toFIG. 1, for purposes of clarity and efficiency the example tag distance calculation system100and corresponding methods, apparatus and articles of manufacture are described herein with respect to an example area101. The example area101may include, but is not limited to a household room, a retail establishment, a shopping mall, a street area and/or an amusement park. Information about an audience member's behavior may be determined/estimated using location information relative to a media source and/or audience member motion information. Location information may include, for example, position information that, when analyzed, may be used to determine the movements of a person or an audience member from one location to another. Location information may also include distances between an audience member and a media source, such as, for example, a home entertainment center, television, and/or a set-top box (STB) that resides in a household. Example location detection devices described below may be worn or otherwise carried by a person or audience member.

The example area101, in which the example methods, systems, apparatus and articles of manufacture of the present disclosure may operate, includes example tags102A,102B worn by respective audience members104A,104B. Tags may include, but are not limited to, bracelets, necklaces, broaches, pendants, belt attachment(s) and/or other relatively small and/or unobtrusive battery powered devices carried by the audience members. The example area101also includes an example media delivery center106to generate media audio signals from one or more speakers108. The example media delivery center106may include one or more media delivery devices (e.g., a television, a radio, etc.) and/or one or more media playback devices (e.g., a DVD player, a VCR, a video game console, etc.). In the illustrated example ofFIG. 1, audio signals emitted from the one or more speakers108propagate throughout the area101. Generally speaking, the speed at which the audio signals propagate is dependent upon atmospheric conditions including air temperature and humidity and will be assumed herein to be 13,041.6 inches per second (331.25 meters per second or approximately 741 miles/hr). In the event the example speaker108emits a sound at time zero (t0), the emitted sound will reach a distance D1at a first time (t1). Similarly, the emitted sound will continue to propagate to distances D2and D3at corresponding times t2and t3.

The example area101also includes one or more base units110. The base unit110may interact with the tags102for battery charging and/or data transfer operations, as discussed in further detail below. Additionally, the base unit110of the illustrated example is configured to work cooperatively with the tags102to substantially continuously generate location information of the audience members104A,104B relative to the location of the example media delivery center106as the audience member104moves among areas within, around, and/or outside the example area101. The base unit110of the illustrated example is configured primarily as a stationary device disposed on or near the media delivery center106to perform one or more media (e.g., television, radio, Internet, etc.) metering methods. Depending on the types of metering that the base unit110(also referred to as a “set meter”) is adapted to perform, the base unit110may be physically coupled to the media delivery center106or may instead be configured to capture signals emitted externally by the media delivery center106(e.g., audio emitted from the example speaker108) such that direct physical coupling to the media delivery center106is not employed.

In the illustrated example, information collected by the base unit110and/or the tags102is provided to a central facility112. In the example ofFIG. 1, a network114is employed to transfer data to/from the example central facility112. The network114may be implemented using any suitable communication system including, for example, a telephone system, a cable system, a satellite system, a cellular communication system, AC power lines, a network, the Internet, etc. The example central facility112ofFIG. 1is remotely located from the area101and is communicatively coupled to the base unit110via the network114. The central facility112may obtain media exposure data, consumption data, media monitoring data, location information, motion information, and/or any other monitoring data that is collected by one or more media monitoring devices such as, for example, the tags102.

In an example implementation, the central facility112includes a server116and a database118. The database118may be implemented using any suitable memory and/or data storage apparatus and techniques. The server116may be implemented using, for example, a processor system similar or identical to the example processor system P100depicted inFIG. 16. In the illustrated example, the server116is configured to store information collected from the tags102and/or base units110in the database118and to analyze the information.

Turning toFIG. 2, an example tag102A,102B may be worn or carried by an audience member (e.g., the audience member104A) to enable determination of the distance the audience member is from the example media delivery center106. The example tag102ofFIG. 2captures audio information that is exposed to the carrier (e.g., audience member104A), reduces, decimates and/or otherwise processes the captured audio information to reduce memory storage and/or processing requirements, and transmits a reduced set of audio information back to the base unit110as one or more packaged RF signals. At least one benefit realized in response to decimating the audio information received by the example tag102A,102B is that battery life is improved as a result of reducing an amount of data transmitted to the base unit110, thereby permitting the example tag102A,102B to operate in an environment for a greater amount of time before requiring recharging and/or battery replacement.

As described in further detail below, the example tag102A,102B initiates a request to determine a distance between the tag102A,102B and the base unit110near an audio source, such as the example speaker108. The tag102A,102B emits an RF initialization pulse, which propagates at the speed of light toward the base unit110, to initiate audio sampling of the example area101. Both the tag102A,102B and the base unit110may begin audio sampling at substantially the same time, and the tag102A,102B triggers the end of audio sampling by sending a subsequent RF signal to the base unit110containing a representation of collected audio data by the tag102A,102B. In some examples, the tag102A,102B is expected to operate in the example area101(e.g., a room, a portion of a street, an amusement park waiting line, etc.), thereby maintaining an opportunity of constant communication and/or accessibility to the example base unit110. In other examples, the tag102A,102B may be removed from the example area101for periods of time. For instance, in the event that the example tag102A,102B is provided to an amusement park attendee, the amusement park may include any number of example areas101in which a distance calculation may be initiated. However, during instances where the amusement park attendee is walking to/from areas of the amusement park, the example tag102A,102B may not be able to communicate with a base unit, such as the example base unit110ofFIGS. 1 and 3. To prevent the example tag102A,102B from wasting battery resources by transmitting one or more sets of collected audio data via an RF transmission, the example tag102A,102B may utilize the example RF transmitter in a bi-directional manner. For instance, after transmitting the initialization RF signal to any available base unit110, the example tag102A,102B may wait for acknowledgement from the base unit110via a base unit RF acknowledgement signal. If the tag102A,102B fails to receive such an RF acknowledgement signal within a threshold amount of time, the tag102A,102B refrains from further audio collection activities for a period of time. However, if the tag102A,102B receives an RF acknowledgement signal within the threshold amount of time, then the tag102A,102B proceeds to capture ambient audio signal data, decimate the captured audio data to reduce an RF transmission bandwidth, and transmit such decimated captured audio data to the base unit110.

The example base unit110processes the received audio data to determine a match between the tag102A,102B audio data and the collected base unit110audio data. The base unit may calculate a number of samples that elapse between the RF initialization pulse and the matching-point of the audio data to determine how much time elapsed between the sound received by the base unit110versus the tag102A,102B. Additionally, because the propagation speed of sound is known, a distance value may be calculated by the base unit110to represent the distance between the tag102A,102B and the base unit110.

In the illustrated example ofFIG. 2, the tag102includes a processor202, a memory204, a timer/counter206, an audio sensor208, a radio frequency (RF) transmitter210, and a battery212. In operation, the example processor202invokes the RF transmitter210to emit an initialization RF signal to be received by the example base unit110ofFIG. 1. The initialization RF signal facilitates data acquisition synchronization between the base unit110and the tag102because, for all practical purposes, both the base unit110and the tag102receive the RF signal at the same time. On the other hand, any sound emitted from the example speaker108propagates at a substantially slower rate than the RF signal, which can provide an indication of distance based on any measured time lag of the audio propagation. In response to receipt of the initialization RF pulse/signal the example base unit110and the tag102to begin accumulating audio within the example area101. After initialization, audio samples are detected and/or otherwise collected by the example tag audio sensor208. The audio sensor208may be a microphone in communication with the processor202to collect audio samples at a sample rate. After some time period during which audio samples are collected, a subset of the collected audio samples is transmitted back to the example base unit110. This subset of samples is used to determine a distance between the tag102and the base unit110. The base unit110also collects audio samples, which are typically received from the audio source108before they are received by the tag102due to closer proximity of the base unit110to the audio source108. However, some of the audio samples collected by the tag102will not be collected by the base unit110due to the propagation delay of sound from the source108to the tag102, as described in further detail below.

After collecting data for a period of time, as set by the example timer/counter206(e.g., five seconds worth of data), the tag102transmits a subset of the data to the base unit110for analysis. The subset of the audio samples that is transmitted back to the example base unit110is less than the total amount of data that is presented to the tag102, thereby substantially conserving battery power. As described in further detail below, the base unit110receives the initialization RF signal to begin collecting data and stops collecting data when the example tag102begins to transmit its subset of collected audio data. The base unit110employs cues from the initialization RF signal and the received subset of audio samples from the tag102to calculate one or more distance values.

Generally speaking, presently existing microphones and corresponding data collection hardware and/or software (e.g., executing on the example processor202) capture audio at, for example, 8000 samples per second (sample rate). Additionally, if the speed of sound is approximately 13,041.6 inches every second, an 8 kHz sample rate may correspond to a distance of 1.6 inches per sample. While a sample rate of 8 kHz allows a sample to be collected once every 125 microseconds (125 μS), such a high sample rate results in a relatively large amount of data to be transmitted by the tag102via the example RF transmitter210. Moreover, such a high sample rate may not be needed when matching one or more sets of collected audio samples from the tag102with one or more sets of collected audio samples from the example base unit110. Thus, the example tag102may send a subset of audio data to the base unit110that is indicative of an audio envelope rather than a detailed audio signature. Furthermore, for instances in which the example tag102is to provide a general indication of relative distance between itself and the example base unit110, high sample rate may not be necessary. As described in further detail below, the methods, systems, apparatus and articles of manufacture described herein employ the audio data envelope collected by the example tag102and an audio data signature collected by the example base unit110to ascertain a relative distance between the example tag102and the base unit110. As used herein, an audio data envelope represents audio data having a smaller amount of information than the data from which it is derived (e.g., an audio signature). Reduction of the information of an audio signature is described in further detail below and may include, but is not limited to decimating an audio signature and/or applying one or more scale factors to an audio signature.

FIG. 3is a block diagram of the example base unit110ofFIG. 1. As shown inFIG. 3, the example base unit110includes a processor302, a memory304, and a plurality of sensors and/or transducers306. In the illustrated example, such sensors and/or transducers306include an RF interface308, an ultrasonic transceiver310, an optical sensor and/or transmitter (e.g., transceiver)312, and an audio transducer314. The following example focuses on a base unit110that includes any of the RF interface308and the audio transducer314, but, as noted, other example base unit(s)110may include additional or alternate structure(s). The example base unit110also includes a remote transceiver316that receives the monitoring data collected and/or processed by the base unit110and/or received by the tag102and sends it to, for example, the central facility112(FIG. 1). The example base unit114ofFIG. 1also includes a correlation engine318, which is communicatively coupled to the processor302as shown to facilitate one or more correlation calculations between tag102audio signals and base unit110audio signals, as described below in connection withFIG. 16. The example correlation engine318may employ any type of statistical and/or correlation algorithm on received data such as, but not limited to a normalized correlation, Pearson correlation coefficients and/or rank correlation coefficients.

The processor302is used to control and/or perform various operations or features of the base unit110and may be implemented using any suitable processor, including any general purpose processor, application specific integrated circuit (ASIC), logic circuit, digital signal processor (DSP), or any combination thereof. For example, the processor302may be configured to receive location information, motion information, audio information and/or media monitoring information. Information collected may be stored in the memory304and communicated to the central facility118either in its collected form or a format for further processing.

The processor302of the illustrated example is configured to control communication processes that occur between the base unit110and other processing systems (e.g., the central facility118). The processor302may cause the remote transceiver316to communicate monitored, collected, calculated and/or raw audio data to, for example, to the central facility118(FIG. 1). Additionally, the processor302and/or the memory of the base unit110may be programmed to carry out the processes ofFIGS. 5and/or7A below.

The memory304is substantially similar or identical to the memory204(FIG. 2) and may be used to store program instructions (e.g., software, firmware, etc.), data (e.g., location information, motion information, media monitoring information, audio samples, etc.), and/or any other data or information.

The RF interface308may be implemented using a transmitter, a receiver, or a transceiver. The RF interface308may be configured to transmit and/or receive location-related information and/or to communicate with the RF transmitter210(FIG. 2) of the tag102. However, to reduce power consumption by the example tag102, the example RF interface308is configured to receive information from, not send information to, the example RF transmitter210, thereby eliminating any need for the tag102to consume battery212power listening for communication(s) from the example RF interface308. Where multiple tags102are present, each tag102is assigned a unique code (e.g., a digital signature of bits, an RF signature, etc.) to enable the base unit110to identify the data it receives as associated with a corresponding tag and to distinguish tags when calculating relative distances therebetween.

The RF interface308is configured to receive RF information from the tag102indicative of one or more sets of collected and decimated audio samples. For example, the RF interface308may receive a set of audio samples that have been packaged into an RF-transmittable format by the example tag102. As described above, where multiple tags102are present, each tag102is assigned a unique code to enable the base unit110to distinguish which tag(s) have initiated a data collection request (e.g., an RF initialization signal) and/or the tag(s) associated with received sets of audio samples. The RF interface308may be implemented using any suitable RF communication device such as, for example, a cellular communication transceiver, a Bluetooth® transceiver, an 802.11 transceiver, an ultrawideband RF transceiver, etc.

The remote transceiver316of the illustrated example is used to communicate information between the base unit110and, for example, the central facility112(FIG. 1). The remote transceiver316is communicatively coupled to the network114and may be implemented using any suitable wired or wireless communication transceiver including, for example, a telephone modem, a DSL modem, a cable modem, a cellular communication circuit, an Ethernet communication circuit, an 802.11 communication circuit, a powerline modem, etc. The remote transceiver316may be used to communicate media monitoring information (e.g., audio samples, codes, and/or signatures), location information, and/or motion information to the central facility112via the network114.

FIG. 4illustrates an example wireless tag timing diagram400indicative of audio samples received by the example base unit110and two example wireless tags, such as the example tags102A and102B ofFIG. 2. In the illustrated timing diagram400ofFIG. 4, a timing row402identifies data sample timing units ranging from t3to t+16timing units. Each timing unit in the example timing row402is indicative of an amount of time that corresponds to a data rate of the tag102. As described above, currently existing microphones and/or corresponding driver hardware/software typically sample audio data at a rate of 8 kHz (although such rates may be superseded with newer technologies developed during the lifetime of this patent). However, in the illustrated example ofFIG. 4, each timing unit (e.g., t1, t0, t+1, . . . , etc.) represents a sample rate decimated by a factor of five (5). The decimation factor described herein is selected as an example value of five for purposes of discussion and not limitation, thus, any other value may be selected. In the illustrated example ofFIG. 4, each timing unit represents a span of 625 μS. As described in further detail below, while the example tag (e.g.,102A) returns one or more subsets of audio data (via the example RF transmitter210) at a decimated rate, thereby reducing the volume of data to be transmitted by the example RF transmitter210, the example base unit110may capture audio data at the same rate or capture at a higher data rate (e.g., 8 kHz) because it is unconcerned and/or less concerned with power savings than the battery powered tags.

In the illustrated example timing diagram400ofFIG. 4, a base unit row404indicates which audio samples occurred at the base unit110at the corresponding timing row402timing unit, a tag102A row406indicates which audio samples occurred at a first tag102A (e.g., a bracelet worn by an audience member) at a corresponding time as indicated by the timing row402, and a tag102B row408indicates which audio samples occurred at a second tag102B at a corresponding time as indicated by the timing row402. The illustrated example timing diagram400reflects an RF initialization signal or packet410to identify when a tag (e.g., tag102A) emitted an indication that the tag102A is beginning to collect audio samples, thereby triggering capturing of audio samples at the base unit. As used herein, an RF signal, such as an RF initialization signal, includes radio frequency energy emitted from a device, while an RF packet includes a radio frequency energy emitted from a device that also includes payload or other information, such as transmitter identification information. The terms signal or packet may be used interchangeably herein. In the illustrated example ofFIG. 4, the tag102A is responsible for the RF initialization signal410, which is indicated by RF1at time t0from the example timing row402. Receipt of RF1by the base unit110causes the base unit to begin saving audio samples to the memory304. RF1also corresponds to the time at which the first tag102A begins saving received audio samples.

To illustrate a relative time in which audio samples arrive at the example base unit110, the first tag102A and the second tag102B, the example timing diagram400represents a series of audio samples using lower case letters “a” through “t.” While the alphabetic representations “a” through “t” could be replaced by an analog audio signal representation(s), such as shown and described below in connection withFIG. 7B, the alphabetic representation is employed herein for ease of explanation. In the illustrated example, the base unit110is closer to the source of the audio samples than the tags102A,102B, and receives audio sample “a” at time t−3(see base unit row404), while tag102A does not receive audio sample “a” until time t−1, and tag102B does not receive audio sample “a” until time t+1, which suggests that tag102B is further away from the base unit110than tag102A. In operation, the tag102B transmits the RF1initialization signal410to indicate the beginning of a distance calculation. The tag102A emits the RF1signal at substantially the same time it begins sampling ambient audio via its audio sensor208at time t0. Additionally, the receipt of the RF1initialization signal410by the RF interface308of the example base unit110is, for all practical purposes, instantaneous due to its speed-of-light propagation. As a result, the tag102A and the base unit110begin collecting data at substantially the same time.

Assuming that the tag102A (corresponding to row406) begins saving audio samples to memory immediately after the RF1initialization signal410, any attempt to compare audio sample “c” with the same audio sample collected by the base unit110(corresponding to base unit row404) will never result in a match. This is true because at the moment the RF1initialization signal410was transmitted by the tag102, the sound energy corresponding to audio sample “c” had already propagated away from the base unit110(on its way to the tag102). Accordingly, any attempt to compare collected audio samples “c” at tag102A with collected base unit audio samples will result in failure and/or wasted processing resources. Furthermore, energy consumed by the tag102A in sampling, storing and/or transmitting audio sample “c” to the base unit110is wasted and represents battery energy that could have otherwise been consumed sending data that has a chance of being matched to audio samples collected by the base unit110.

To prevent transmitting wasted audio samples, the example tag102A employs the timer/counter206to wait for a delay time TDbefore saving audio sample data to memory204. The example delay time TDmay be set to any value, such as a value that corresponds to the maximum size of a room or other monitored area of interest. For example, in the event that an analyzed room, such as the example area101ofFIG. 1, is 12-feet long, then the delay time TDmay be set for 11 milliseconds (mS), assuming that the speed of sound is 13,041.6 inches/second (not including atmospheric calibration). In that case, the chances of both the base unit110and any tag102in the example area101storing the same audio signals are relatively high versus when the delay time TDis set to any lower value. Upon the expiration of the delay time TD, the example tag102begins saving audio signals as data samples to the memory204at a start time Tsand stops saving data samples to the memory at a finish time TF. In the illustrated example ofFIG. 4, the start time Tsoccurs at time t+5and the finish time TFoccurs at time t+14. In other words, the example tag102saves ten (10) data samples to the memory204as a set, and sends the set of data samples (i.e., audio samples “g” through “p”) to the example base unit110to, in part, signal to the base unit110that audio sample data acquisition should stop.

At this point, the base unit110has received the initialization signal RF1, collected its own set of audio samples “d” through “r” (which are stored in a memory as data samples), has received the set of data samples from the tag102A (i.e., audio samples “g” through “p”), but otherwise has no knowledge of how far the tag102A is from the base unit110. To calculate how far the tag102A is from the base unit110, the base unit110searches the received set of data samples from the tag102A (i.e., audio samples “g” through “p”) for a match corresponding to its own data samples. In the event that the example base unit110identifies that a match exists at its own data sample corresponding to audio sample “g,” which was received by the base unit at time t+3, the base unit110now has sufficient information to calculate a difference between time t+3and the time at which the initialization signal RF1was sent. In other words, the base unit110subtracts t+3from t+5to yield a difference of two time units. The number of time units may then be multiplied by the time per each unit, which may further be multiplied by the speed of sound to determine a relative distance between the base unit110and the tag102. For example, in the event that each time unit t corresponds to 0.625 mS, then 1.25 mS (i.e., two time units of 0.625 mS each) multiplied by 13,041.6 inches per second yields a relative distance of 16.3 inches. After determining a distance between the tag102and the base unit110, the stored set of audio samples from the tag102A (i.e., “g” through “p”) may be analyzed to identify the media content. Similarly, the stored set of data samples from the base unit110(i.e., stored audio samples “d” through “r”) may be analyzed to identify whether the tag102A data samples are the same as the base unit110data samples.

While the example tag distance calculation system100has been illustrated inFIGS. 1,2and3, one or more of the interfaces, data structures, elements, processes, user interfaces, and/or devices illustrated inFIGS. 1-3may be combined, divided, re-arranged, omitted, eliminated and/or implemented in any other way. Further, the example tags102A,102B, the example media delivery center106, the example base unit110, the example central facility112, the example server116, the example database118, the example processor202, the example memory204, the example timer/counter206, the example audio sensor208, the example RF transmitter210, the example processor302, the example memory304, the example sensors/transducers306, the example RF interface308, the example ultrasonic transceiver310, the example optical sensor/transmitter312, the example correlation engine318and/or the example audio transducer314ofFIGS. 1-3may be implemented by hardware, software, firmware and/or any combination of hardware, software and/or firmware. Additionally, as described in further detail below, the example test manager1102, the example trigger monitor1104, the example tag interface1106, the example base unit interface1108and/or the example delay period adjustor ofFIG. 11may also be implemented by hardware, software, firmware and/or any combination of hardware, software and/or firmware. Thus, for example, any of the example tags102A,102B, the example media delivery center106, the example base unit110, the example central facility112, the example server116, the example database118, the example processor202, the example memory204, the example timer/counter206, the example audio sensor208, the example RF transmitter210, the example processor302, the example memory304, the example sensors/transducers306, the example RF interface308, the example ultrasonic transceiver310, the example optical sensor/transmitter312, the example correlation engine318, the example audio transducer314, the example test manager1102, the example trigger monitor1104, the example tag interface1106, the example base unit interface1108and/or the example delay period adjustor may be implemented by one or more circuit(s), programmable processor(s), application specific integrated circuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)) and/or field programmable logic device(s) (FPLD(s)), etc.

FIGS. 5,6,7A,9,12,14,15A and15B illustrate example processes that may be performed to implement the example tag distance calculation system100ofFIGS. 1-4and11. The example processes ofFIGS. 5-7A,9,12,14,15A and15B may be carried out by a processor, a controller and/or any other suitable processing device. For example, the example processes ofFIGS. 5-7A,9,12,14,15A and15B may be embodied in coded instructions stored on any tangible computer-readable medium such as a flash memory, a CD, a DVD, a floppy disk, a read-only memory (ROM), a random-access memory (RAM), a programmable ROM (PROM), an electronically-programmable ROM (EPROM), and/or an electronically-erasable PROM (EEPROM), an optical storage disk, an optical storage device, magnetic storage disk, a magnetic storage device, and/or any other tangible medium. Alternatively, some or all of the example processes ofFIGS. 5-7A,9,12,14,15A and15B may be implemented using any combination(s) of ASIC(s), PLD(s), FPLD(s), discrete logic, hardware, firmware, etc. Also, one or more of the example processes ofFIGS. 5-7A,9,12,14,15A and15B may instead be implemented manually or as any combination of any of the foregoing techniques, for example, any combination of firmware, software, discrete logic and/or hardware. Further, many other methods of implementing the example operations ofFIGS. 5-7A,9,12,14,15A and15B may be employed. For example, the order of execution of the blocks may be changed, and/or one or more of the blocks described may be changed, eliminated, sub-divided, or combined. Additionally, any or all of the example processes ofFIGS. 5-7A,9,12,14,15A and15B may be carried out sequentially and/or carried out in parallel by, for example, separate processing threads, processors, devices, discrete logic, circuits, etc.

The example process500ofFIG. 5begins with the processor302of the example base unit110monitoring for an RF initialization signal from one or more tags102A via the example RF interface308(block502). If no RF initialization signal is received, the example process500ofFIG. 5waits. Otherwise, after the RF interface308receives the RF initialization signal, the example processor302invokes the audio transducer314to begin storing received audio samples to the memory304(block504). As described above, audio samples that are captured and stored to a memory are referred to herein as data samples. The example RF initialization signal may include identification information regarding which tag102A is initiating a distance measurement. Each tag102A,102B may include a tag identifier that is embedded with the example RF initialization signal, such as RF1as described above in connection withFIG. 4.

The example base unit110continues to store the audio samples it detects via the example audio transducer314to the memory304(block506), and stops recording audio samples upon receipt of an RF transmission indicative of tag102A,102B data samples (block508). In other words, instances of distance measurement between a tag102A,102B and the base unit110are invoked by each tag102A,102B that may be present in the example area101. By allowing each tag102A,102B to invoke nearby base unit(s), the tag(s)102A,102B may operate without continuous signal monitoring, which minimizes additional power consumption of the tag(s)102A,102B. In other examples, the base unit110does not wait for the RF transmission indicative of the tag102A,102B and, instead, collects a fixed amount of audio information. In such examples, block506is not needed.

The example base unit110parses the received data samples that were embedded in the RF signal transmitted by the tag102A,102B to identify a portion of audio samples that match the audio samples collected by the base unit (block510). During base unit audio sample storage, the example base unit110stored a representation of the audio signal (e.g., one or more acoustic energy values, one or more acoustic frequency values, a series of values from a microphone, etc.) and a time (time stamp) at which the audio signal was saved to the base unit memory as one or more data samples304. The example processor302counts a number of data samples that were stored between (1) the RF initialization signal plus the time delay (TD) and (2) the point at which the base unit110audio signals match the tag102audio signal representations (block512).

Each data sample saved by the base unit110is collected at a known frequency and is matched with a corresponding time stamp. For example, if the base unit110sample rate is set equal to that of the tag102A (e.g., 1600 Hz), then each data sample is separated from an adjacent data sample by a time of 625 μS. As such, the number of data samples is multiplied by the time per data sample by the example processor302, which is further multiplied by the speed of sound to calculate a distance value (block514). The distance value calculation is stored in the memory304along with a time stamp (block516) and the example base unit110returns to block502to await another RF initialization signal.

The example process600ofFIG. 6illustrates operation of the example tag102A or102B during a distance calculation. In the illustrated example ofFIG. 6, the example processor202invokes the example timer/counter206to expire after a predetermined time period, such as a duration of every 10 minutes, for which a distance calculation is desired (block602). While the time period has not expired (block602), the example process600waits in a loop. However, when the example timer/counter206signals to the processor202that the time period has expired (block602), the example processor202of the tag102invokes the example RF transmitter210to transmit an initialization signal to the base unit110(block604).

As described above, the example tag102A or102B does not immediately start sampling and/or storing ambient audio samples to memory (i.e., storing audio samples to memory as data samples) immediately after transmission of the RF initialization signal because, in part, some of the initial audio samples would have already propagated past and has not been stored by the base unit110on its way to the tag102A or102B. As a result, the earliest audio samples collected by the tag102A or102B would never match audio sample(s) received at and/or stored by the base unit110. Additionally, transmitting one or more data samples (i.e., audio samples collected and stored to a memory) from the tag102A or102B to the base unit110that have no possibility of resulting in a match, which needlessly consumes tag102A or102B battery resources. To minimize and/or eliminate wasted processing and/or transmission resources of the tag102A or102B, the example processor202invokes the timer/counter206to initiate a delay time TD(block606). In effect, the delay time TDallows the example tag102A or102B to “catch-up” with the audio samples captured by the example base unit110. If the timer/counter206does not indicate that the delay time TDhas expired (block608), then control loops to block608until the expiration of the delay time TD.

When the delay time TDexpires (block608), the processor202causes the example audio sensor208to begin capturing audio samples (i.e., ambient audio information) at the sample rate designated by the tag102A or102B hardware configuration (block610). As described above, industry standard audio capture devices and/or corresponding audio data acquisition software may capture at a default data rate, such as 8 kHz. In some instances, modification of audio data acquisition hardware and/or corresponding software may be cumbersome and/or difficult to access. In other instances, off-the-shelf audio data acquisition solutions may be desired to maintain simplicity and minimize cost of the example tag102A or102B. While processing and/or storage of audio data samples at a higher data rate may create a greater demand for battery power resources, such demands are of less importance than the substantially greater drain of battery power resources typically associated with packaging and transmission of RF data from the example tag102A or102B. As such, efforts to decimate collected audio samples are applied to the stored data samples before they are prepared for RF transmission, as described in further detail below.

If the finish time TFhas not yet been reached (block620), then the example process600ofFIG. 6returns to block610and the process continues to collect ambient audio samples. On the other hand, when the finish time TFhas been reached (block620), which indicates that the time period for audio sample acquisition has ended, the example processor202applies a bandpass filter (block632). The bandpass filter may be facilitated by way of software executing on the example processor202or by way of one or more solid state filters (not shown). Bandpass filters may operate between, for example, 300 Hz to 3 kHz, and/or any other value(s) of interest. A scale factor (e.g., adjustable, fixed, variable, proportional to a percentage of source data, etc.) may be applied to the decimated audio data sample set (block634) to further reduce an amount of data transmitted from the tag102A,102B to the base unit110. For example, while many microprocessors and/or microcontrollers available accommodate register sizes of any number of bits (e.g., 8-bit, 12-bit, etc.), such full resolution of bits is not always needed for sufficiently accurate distance calculations and/or estimations. Accordingly, one or more scale factors may be applied to the data samples to reduce a number of bits needed per data sample (block634).

In the illustrated example ofFIG. 6, the processor202decimates the ambient audio data stored in the memory204(block636). Data decimation may occur by, for example, accessing every Nthaudio data sample stored in the example memory204, where N may be an integer value. For example systems100that employ audio sampling hardware at a rate of 8 kHz (i.e., 8000 samples of audio information collected every second), which yields a resolution of distance calculations within 1.6 inches between audio samples, the example tag102A or102B may employ a decimation factor (N) of, for example, twenty (20) for circumstances where greater resolution is not necessary. Any other decimation factor (N) may be employed, without limitation. An example decimation factor of twenty (20) substantially decreases the amount of audio data samples transmitted from the tag102A,102B to the base unit110. While any value of N may be employed as the decimation factor to reduce the transmitted data volume from the tag102A,102B, higher decimation factors may affect the resolution of one or more calculated distance values of the tag102A,102B location. In other words, application of a decimation factor (N) includes a tradeoff between battery conservation with resolution.

Additionally, the example processor202calculates or determines an absolute value of the data samples saved to the example memory204(block638), which may simplify binary representation(s) of the collected data samples. In other words, using the absolute value of the data samples (block638) eliminates a need to process negative signage of one or more binary values.

The decimated set of data samples is then transmitted to the base unit (block670), and control returns to block602. Generally speaking, the example base unit110receives tag102A,102B data, receives audio samples acquired from the audio transducer314, and then processes the received data to determine a distance value between the tag102A,102B and the base unit110. In operation, after the example base unit110receives the tag102A,102B data samples, the received tag102A,102B data samples are expanded in a manner consistent with a decimation factor applied by the tag102A,102B. In the event that the example tag102A,102B applied a decimation factor of 20, then the base unit110reverses the decimation by expanding by the inverse of the factor. A moving average may be applied by the example base unit110, such as an N-point moving average. In some examples, a moving average N of 20 produces satisfactory results, but any other value may be employed as desired. The example expansion and moving average produces curve data suitable for comparison purposes. As such, if the example tag102A,102B originally acquired audio samples at 8000 samples per second prior to decimating corresponding stored data samples by a factor of 20 (e.g., thereby transmitting 400 data samples), then the aforementioned expansion and moving average produces an 8000 sample per second data set suitable for one or more comparison(s).

As described above, the example base unit110also acquires audio samples from the audio transducer314. In operation, the example base unit110subtracts each data sample (acquired from a corresponding audio sample) from a moving average of N past and current data samples. In some examples, a moving average value N of 8 produces satisfactory results, but any other value may be employed as desired. After determining an absolute value, the example base unit110applies a moving average of N points, such as 20. While an example moving average value N of 20 produces satisfactory results in certain environments, any other moving average value N may be employed as desired.

Prior to transmitting one or more decimated data sample sets to the example base unit110, the example tag(s)102A,102B may also employ one or more compression techniques to the decimated and/or scaled data samples prior to RF transmission in an effort to further reduce an amount of transmitted data. Compression techniques may include, but are not limited to commercial compression techniques (e.g., gzip, which is free software released under the GNU General Public License) and binary run-length encoding.

In some examples, additional battery conservation may occur by eliminating the bandpass filter hardware and/or eliminating one or more bandpass filter calculations performed by the example processor202of the tag102A,102B. Although the effect of bandpass filtering may facilitate proper data processing by the tag102A,102B (e.g., removal of DC components, etc.), the computationally-intensive process of bandpass filtering may be replaced with a moving average process. In one example, a moving average is subtracted from the current data sample. The moving average may be calculated using Y data samples, which includes the current data sample and Y−1 prior data samples. For some example circumstances, a moving average value Y of 8 yields satisfactory results, but any other value(s) may be employed, as desired. During operation, the example moving average using the prior Y data samples may replace block632of the process600ofFIG. 6.

In the event that more than one tag102A,102B operates in the example area101at the same time, the example base unit110may process each distance measurement request separately. For example, upon receipt of an RF initialization signal from the tag102A, the base unit110may allocate processing resources, such as the processor302, and memory304to store and/or process audio samples captured by the audio transducer314. Further, if tag102B also transmits an RF initialization signal, the base unit110may allocate the processing resources with a separate section of the memory304in which to store audio samples (as data samples) captured by the audio transducer314. In other examples, any audio samples collected by the base unit110and stored to the memory304(as data samples) may be shared for overlapping time period(s), thereby conserving memory resources and may further reduce processing demands imposed upon the example processor302. Each set of data captured and/or otherwise processed by the base unit110may be further associated with an indication of the tag102A,102B responsible for a distance calculation request.

The example process700ofFIG. 7Aillustrates correlation based matching between data samples collected at the tag102A,102B and data samples collected at the base unit110. The example process700ofFIG. 7Amay be executed to, in part, satisfy some or all of the procedures described in block510of the example process500ofFIG. 5. As described above, the data samples stored in the memory304of the base unit110begin at the moment in time at which the RF initialization signal (see410ofFIG. 4) was transmitted by the example tag102A or102B. However, because a portion of the earliest audio samples (and corresponding data samples) captured by the example tag102A or102B lack parity with the audio samples (and corresponding data samples) captured by the example base unit110, the example correlation engine318establishes a base unit data sample starting point based on the delay or dwell time TDused by the example tag102A or102B (block702). The dwell time TDallows any subsequent analysis, comparison and/or calculation of correlation values between the collected tag102data samples and the collected base unit110data samples to overlap with each other.

Turning briefly toFIG. 7B, a base unit audio waveform750(e.g., a plurality of audio samples in the example area101) is captured by the base unit110at a time earlier than a tag audio waveform752due to the fact that the base unit110is closer to the audio source108than the tag102A. At time t0, an RF initialization pulse transmitted by the example tag102A causes the base unit110to begin capturing audio samples. Additionally, at time t0, the tag102A is exposed to a portion of the audio waveform that has already passed the base unit110and may not be in the memory of the base unit110. As described above, the example time delay (TD) is selected to correspond to a maximum desirable distance from the base unit110. In the event that the tag102A,102B is at a distance less than the distance corresponding to the maximum TDvalue, a portion of the tag102A,102B data samples prior to TDwill be present in the base unit110memory304. In other examples in which the tag102A,102B is near or immediately adjacent to the base unit110, all of the data samples stored by the tag102A,102B will also likely be stored in the base unit110memory304. In any event, to ensure certainty in comparisons and/or calculations with base unit110data samples and tag102A,102B data samples, comparisons only occur with such data that was collected after the expiration of TD. As such, the example tag102refrains from saving data samples (corresponding to audio samples of the waveform752) until after the delay time TDhas expired to ensure that attempts to compare the example base unit audio waveform750and the example tag audio waveform752for a matching point(s) are successful.

While an overlap between the tag audio waveform752from the tag102A and the base unit waveform750from the base unit110may allow for an identification of a match during one or more comparisons therebetween, which may illustrate a propagation time delay from the audio source to the tag102A, there may be some circumstances in which it is desired to identify a strong lack of correlation. For instance, a strong lack of correlation is expected when audio samples captured by the tag102A have not also been captured by the base unit110, such as at an example offset point754ofFIG. 7B. In the event that an attempt is made to calculate a correlation between the offset point754from the tag audio waveform752and t0of the base unit audio waveform750, then a low, zero or negative correlation value is expected. However, upon shifting an analysis position within the tag audio waveform752over to the expiration of the time delay TD(756), an attempt to calculate a correlation between a tag data starting point TSPand t0of the base unit audio waveform750will result in a positive correlation value due to the similarity and/or exactness of the two waveforms (i.e., a match). In other words, circumstances in which a relatively strong negative correlation value transitions into a positive correlation value may be indicative of a point at which the base unit waveform750and the tag waveform752match.

In some examples, a value of TD(756) may be set to 300 time units, which corresponds to approximately 41 feet when each time unit occurs at a frequency of 8 kHz. However, in other examples a wide range of TDvalue(s) may be employed to ensure a peak in the correlation value(s) is detected. Once a TDvalue is chosen, such as an example value of 300, a compatible search range may be employed during the comparison (e.g., −300 to 0). In the event of uncertainty and/or concern for variability of system100performance, then the search range may be extended to include a number of both positive and negative time unit values (e.g., a range between −300 and 20, a range between −300 and 50, etc.). For circumstances in which the tag102A,102B and the base unit110data are swapped, a range between −300 and +300 may be employed for convenience. Range searches may be performed on tag102A,102B data samples and/or base unit110data samples, without limitation. However, in the event that one or more range searches are performed by the base unit110, the example tag102A,102B does not need to consume additional battery power resources.

In the illustrated example ofFIG. 7C, a schematic illustration730of base unit110data samples732and tag102A,102B data samples734are shown relative to a timeline736. Example base unit110reference samples732begin with sample Rewhile example tag102A,102B query samples734begin with sample Qc, each at a time of 1 time unit. The example base unit110reference samples732represent a series of 4,000 data samples spaced ten (10) audio samples apart, which corresponds to a total width of 40,000 data samples when five (5) seconds of data are collected at 8,000 samples per second. Similarly, the example tag102A,102B reference samples734represent a series of 4,000 data samples spaced ten (10) audio samples apart from each other, which corresponds to a total width of 40,000 data samples when five (5) seconds of data are collected at 8,000 samples per second. Although the tag102A,102B reference points734will have matching reference samples to the base unit110, one or more differences caused by, for example, noise and/or distortion may be present.

In the illustrated example ofFIG. 7C, TDis set to a value of 10, and a sequence of tag102A,102B data is taken starting at sample Qm. Any number of subsequent tag102A,102B data may be used as a subset of samples for comparison purposes (e.g., Qm, Qn, Qo, Qp, etc.). In the event that a search range from −3 to +3 time units is conducted, which may analogous to the example range of −300 to +300 described in connection withFIG. 7B, then the subset of tag102A,102B data samples may be compared to reference points centered around the time of 11 time units (i.e., the initialization time+TD=1+10) (e.g., R1, Rm, Rn, etc.). In other words, the subset of samples Qm, Qn, Qo, Qp, etc. are iterated during one or more comparisons with offsets of the reference points, as shown by an iteration sequence738. Any search range value and/or step size may be employed by the methods, systems, apparatus and articles of manufacture described herein. For instance, in the event that an increase in comparison speed is desired, steps may be set to five (5) samples (i.e., approximately 8 inches) in view of a lower resolution tradeoff.

As shown in the illustrated example ofFIG. 7C, the base unit110reference samples Rm, Rn, Rocorrespond to a local maximum correlation value, thereby indicating a likely match between audio samples collected at the base unit110and the tag102A,102B. The highest correlation value occurs at a relative offset of −2 samples, which further corresponds to a distance of 3.262 inches (assuming each sample equals 1.631 inches based on a speed of sound of 13,041.6 inches per second).

Returning toFIG. 7A, the example correlation engine318selects TDrange value to increase the likelihood of waveform overlap during one or more comparisons between the base waveform750and the tag waveform752. A curve shift step size is established and/or otherwise selected (block706), which dictates the span of sample time unit sizes analyzed during one or more comparison(s). For example, if each sample was captured at 8 kHz, then a step size of 5 time units corresponds to a physical distance of approximately 8 inches (i.e., the distance that sound can travel in five time units).

For each step, a set of base unit data samples and tag data samples are provided to the example correlation engine318(block708) and the example correlation engine318calculates a corresponding correlation value associated with the time unit (block710). Data used by the example correlation engine318may occur by way of, for example, 4000 data samples having a separation of 10 time units therebetween. In other words, while an original example time unit of five (5) seconds at 8000 samples per second produces 40,000 data samples, the example separation of 10 time units substantially reduces the data load. Such a reduced data load reduces computational burdens on the example base unit110. For example, if the first set of base unit data samples and tag data samples are provided to the correlation engine318at data sample number 80 (e.g., based on the selected starting point (block702)), then data sample number 80 has a corresponding distance based on the distance sound travels for 80 units of time. Assuming, for purposes of explanation and not limitation, each unit of time corresponds to an 8 kHz data capture rate, then sound travels approximately 1.63 inches per sample period. Accordingly, 80 data samples corresponds to a distance of 10.9 feet. The example processor302counts a number of data samples that occurred between (1) the RF initialization signal plus the time delay (TD) and (2) the point at which both waveforms (i.e., the tag102A,102B waveform752and the base unit110waveform750) match with the highest correlation value. Each such counted sample corresponds to 1.63 inches of separation between the tag102A,102B and the base unit110. If all the tag waveform752data samples have not been compared and/or correlated to one or more portions of the base unit waveform750(block712), the tag data samples are shifted by the step size (block714) and control returns to block708. Otherwise, after all tag data samples have been calculated to find a corresponding correlation value (block712), the example correlation engine318identifies a highest relative correlation value (block716).

Briefly turning toFIG. 7D, an example list of correlation values770calculated by the correlation engine318are shown. The example list of correlation values770includes a time unit column772and a corresponding correlation value column774. As described above, a higher correlation value is indicative of a greater likelihood that the data from the base waveform750and the tag waveform752match, while lower correlation values represent a lower likelihood that the waveforms match. As the example correlation engine318calculated and shifted through the data, as described above in connection withFIG. 7A, rows of correlation values with corresponding time units were saved to the memory304of the example base unit110. Time unit93(a relative time) is identified by the example correlation engine318to have the highest relative correlation value within the list of correlation values770(block718). Accordingly, the time unit93associated with the highest correlation value is deemed to represent the distance that the tag102was from the base unit110. In other words, the tag102was 12.6 feet away from the base unit110(i.e., 93 relative time units multiplied by 1.631 inches per time unit yields approximately 12.6 feet).

For circumstances in which the example area101includes a room having substantial echo, a highest correlation value may not necessarily represent a match between the base waveform750and the tag waveform752. In the illustrated example ofFIG. 8, an example list of correlation values800has a time unit column802and a correlation value column804and spans from time unit80through time unit180. As described above, time unit93illustrates a local maximum correlation value of 0.352820, which is indicative of a match between audio data from the base unit waveform750and the tag waveform752. However, in the event that the example tag102collects audio signal data for a duration of, for example, five (5) seconds, then one or more echoes may occur in the example area101. In particular, time unit168of the example list of correlation values800illustrates a local maximum correlation value of 0.368839. In the event that the example area101is a room of twelve by twelve feet, then the local maximum at time unit168is an unrealistic indication of a match because it corresponds to approximately 22.4 feet. Accordingly, the local maximum correlation value at time unit168is likely the result of an echo.

To combat and/or eliminate false positives as described above, the methods, systems, apparatus and articles of manufacture described herein may employ a threshold value limit of acceptable time units in which to identify a local maximum correlation value. Threshold values for time units may be established based on advanced knowledge of one or more example area(s)101in which the tag102may operate. For circumstances where the tag(s)102will be used in relatively small rooms, such as 10′×10′ rooms, threshold values for the time unit may be set at or around74time units. On the other hand, for circumstances where the tag(s)102will be used in larger rooms, such as 15′×15′ rooms, threshold values for the time unit may be set at or around110time units.

In other examples, the example methods, systems, apparatus and articles of manufacture described herein identify and/or eliminating false positives caused by echo phenomenon by disqualifying correlation peaks at a later time regardless of the duration of such peaks and/or the magnitude of the correlation value at such peaks. For example, echo suppression may occur by way of evaluating correlation value results in a sequential manner from a closest distance to a farthest distance of interest. In the event of a first local maximum correlation peak at a first time (i.e., the first time corresponds to a highest correlation value when compared to all prior times), the first time is deemed to be the desired maximum if it remains higher than N time samples following thereafter (e.g., for 30, 50 and/or 100 time samples, where each time sample is 1/8000 seconds). As such, even if a higher correlation value is detected at a later time (e.g., farther away), such later higher correlation values are deemed to be associated with one or more echo phenomena and ignored. In other words, all other peaks that may occur at a later time are, in effect, locked out from consideration. For instance, if another distance estimate exhibits a second local maximum correlation value having a higher magnitude, the second local maximum correlation value is not deemed to be a valid match of waveforms (750,752) because it was locked out based on the first local maximum. A sufficient number of time samples N may be determined and/or otherwise established in any manner, including empirical tuning. For example, values of N may include, but are not limited to 30, 50 and 100, which correspond to distance values of 4 feet, 7 feet and 14 feet, respectively when considering a speed of sound at 741 miles per hour.

The example system100may also accommodate different types of microphones employed by the tags102A,102B and/or base unit110. Example microphones may exhibit and/or be constructed with a particular polar pattern, thereby affecting directional sensitivity to sound. For example, unidirectional polar pattern microphones excel at capturing sounds from a relatively narrow degree range, while omnidirectional polar pattern microphones respond to a relatively wider degree of incident sound energy. Based on the type of microphone(s) employed by the example tags102A,102B and/or the example base unit110, decimation rate(s), scaling threshold(s) and/or correlation value threshold(s) may be adjusted accordingly.

The example tag distance calculation system100may also be used to identify participant presence within a room for circumstances in which distance calculations are not needed. As described above, higher correlation values represent greater similarity between captured tag102audio and base unit110audio signals. Threshold correlation values may be empirically determined for one or more example area(s)101to indicate whether a tag (and its wearer) are present within the example area(s)101by virtue of the magnitude of the correlation value.

The example tag distance calculation system100may also be used to distinguish audience member exposure from audience member consumption. Generally speaking, audience member exposure to media content indicates that the audience member was proximate to the media content, but not necessarily engaged in listening and/or watching the media content. Audience member consumption, on the other hand, reflects media content with which the audience member is engaged and/or to which the audience member is paying attention.

The example process900ofFIG. 9begins with the base unit110analyzing collected and processed tag102A,102B data and base unit audio data for an indication of whether the tag102A,102B has moved (block902). If not, then the base unit110and/or system100may determine that there has been no exposure and/or consumption of media content that is emitted by the example media delivery center106via the example speaker108(block904). On the other hand, in the event that the base unit110analyzes the collected and processed tag102A,102B data and base unit data to determine tag movement has occurred (block902), then the base unit110may further compare the magnitude of the tag102A,102B movement with one or more threshold values (block906). For example, movement within three (3) to seven (7) feet may be indicative of an audience member that is exploring a museum from room to room and dwelling for a period of time to engage with an informational kiosk and/or a presenter. In such example scenarios, the example base unit110may determine that exposure and consumption of media content has occurred (block908). On the other hand, in the event that an audience member exhibits substantial movement within an example area101, such as a waiting queue for an amusement park ride, then the example base unit110may determine that exposure (e.g., to an overhead television) has occurred, but consumption of such media has not occurred (block910).

As described above, some applications related to audience member monitoring attempt to synchronize an action between the tag and the base unit, such as the example tags102A,102B and the example base unit110ofFIGS. 1-3. For example, if a tag emits an RF initialization chirp at random and/or periodic times in an effort to initiate a data collection action with a nearby base unit, then the tag may wait for an acknowledgement response signal/packet (an ACK signal/packet). In some examples, the ACK packet contains identifying information related to the base unit and payload information to be processed by the example tags102A,102B. Once the tag determines that a base unit is within communication distance, the tag and base unit attempt to capture audio information of the environment at the same time. The audio information collected from the tag is matched to the audio information collected from the base unit as a matching pair, and may further be analyzed at a later time (e.g., by the central facility112) to determine where the user associated with the tag was located, the distance between the tag and the base unit, and/or identification of the media collected by the tag and/or base unit (e.g., audio signature analysis, audio code(s) detection, etc.). Such post-collection analysis presents matching accuracy issues when the samples collected by the tag differ from the samples collected by the base unit. In particular, post-collection analysis may be difficult when the duration of the collected audio information by the base unit differs from the duration of the collected audio information by the tag. For the examples that follow, the example tag102A is employed for purposes of discussion rather than limitation. In other words, the example tag102B and/or one or more additional/alternate tags may be employed with the methods, systems, articles of manufacture and apparatus described herein.

FIG. 10includes an audio waveform1002A received by the example tag102A and the same audio waveform1002B received by the base unit110to illustrate the discrepancies between the information (e.g., data samples saved to a memory) collected by the tag102A,102B and the information collected by the base unit110. The example audio waveform1002A,1002B is, for example, a portion of audio energy emitted by the speaker108located near the example base unit110and tag102A. More specifically, discrepancies between the tag102A,102B and the base unit110occur when actions (e.g., start recording, stop recording) therebetween are not synchronized in time. In the illustrated example ofFIG. 10, the tag102A transmits an RF initialization packet (or packet) at time t01004to determine if any base units are nearby. The base unit110receives the RF initialization packet at time t0(1006) because, for all practical purposes, the propagation speed of the RF initialization packet from the tag102A to the base unit110is instantaneous. However, because the example base unit110is located very near to the source of audio, the waveform is shifted, which is represented by time markers (e.g., t0, t1, t2, etc.) of the waveform1002B appearing farther to the right when compared to the time markers of the waveform1002A. To let the tag102A,102B know that the base unit110is within communication range, the base unit110transmits an ACK packet at time t11008, which is received by the tag at time t11010.

After the tag receives the ACK packet at time t11010, which may contain payload information of varying lengths (e.g., information to identify the base unit), the tag102A,102B begins collecting audio samples after a tag delay period of time DTAG1012. The delay period of time DTAG1012may be caused by the tag circuitry (e.g., tag processor202) processing the received ACK packet. In other examples, DTAG1012is caused by a program counter position of the tag processor202. In other words, DTAG1012may vary based on a number of factors such that the time at which the example tag actually starts recording audio (e.g., at time t4)1014is not predictable.

Although the base unit110sends the ACK packet1008at time t1to trigger the beginning of audio data collection, the example tag102A does not begin audio data collection until time t4due to tag processing delays DTAG1012. As such, the example base unit110collects a portion of the audio waveform1002B starting at time t1(1008) while the example tag102A collects a portion of the audio waveform1002A starting at time t4(1014). As described above, future attempts to match the collected data samples between the tag102A and the base unit110may be complicated in view of the dissimilar starting times and/or differences in the overall duration of the collected audio between the base unit102A and the base unit110.

In the illustrated example ofFIG. 10, the tag102A transmits an RF signal or packet (e.g., a packet including information identifying the tag102A) to stop recording audio1016(at time t10), which also causes the base unit110to stop recording audio1018(at time t10). The example tag102A,102B recorded audio data for six (6) time units (i.e., t4through t10), which is represented by duration A1. On the other hand, the example base unit110recorded audio data for nine (9) time units (i.e., t1through t10), which is represented by duration A2. Attempts to later match durations A1and A2are, thus, complicated because the duration of A1does not equal the duration of A2, and because the example tag102A and the example base unit110do not begin recording at the same time. In the event that the example tag102A stores a number of audio recordings (e.g., storing audio until a buffer storage threshold is reached), the receiving base unit110and/or the example entral facility112needs to identify a match between audio recordings captured and stored by the tag(s) and audio recordings captured by the base unit(s). Attempts to determine which instances of collected tag audio occurred at the same time as instances of collected base unit audio become difficult if the tag(s) batch their stored instances of audio information. In such cases, a match may need to occur between numerous tag(s) and number base unit(s) at numerous dates/times.

In some examples, the tag(s) employs a real time clock to date/time stamp audio information at the time it is collected and stored to allow each instance of stored tag audio information to be stored with each instance of stored base unit audio information. Additionally, the tag(s) embed tag identification information in the collected audio information. In such cases, the tag(s) must consume additional power to embed and transmit extra data via RF signals to the base unit(s). Further, the real time clock consumes additional power from the tag, which reduces an amount of time it can operate in the field prior to a recharge.

As described in further detail below, the example base unit110may attempt to match collected data samples with data samples collected by one or more tags. Rather than attempt to match tag data samples with base unit audio samples by examining analog or digital waveform characteristics (e.g., corresponding audio energy peaks, audio energy lows, etc.), the example base unit110may determine a match based on a similar or identical duration of the collected data samples. For example, if the base unit110collects 2000 milliseconds of data samples and receives data samples from two tags, one having 2000 milliseconds of duration and the other having 2020 milliseconds of duration, then the base unit can identify a match between its collected data samples and those from the tag having 2000 milliseconds of duration.

FIG. 11is a block diagram of an example calibrator1100that may be used with the example base unit110and example tags102A,102B ofFIGS. 1-3. In the illustrated example ofFIG. 11, the calibrator1100includes a test manager1102, a trigger monitor1104, a tag interface1106, a base unit interface1108, and a delay period adjustor1110. In operation, the example test manager1102verifies that a tag to be calibrated is communicatively connected to the example trigger monitor1104via the example tag interface1106. Additionally, the example test manager1102verifies that a base unit to be calibrated with the tag is communicatively connected to the example trigger monitor1104via the example base unit interface1108. Communicative connection between the trigger monitor1104and the tag and/or the base unit, such as the example tag102A,102B ofFIG. 2and the example base unit110ofFIG. 3, may include, but is not limited to connection of trigger monitor probes to circuit points of the example tag102A,102B and base unit110. The example trigger monitor1104, in operation, monitors one or more of the example tag102A,102B and base unit110for one or more trigger actions occurring thereon. For example, the trigger monitor1104may be an oscilloscope, a logic analyzer or similar device capable of identifying circuit logic state(s), voltage fluctuation(s) and/or other electrical and/or physical phenomena. Circuit points of the example tags and/or base unit(s) may include one or more pins of the example processor202of the tag102A,102B and/or one or more pins of the example processor302of the base unit110.

Additionally or alternatively, the example test manager1102may be communicatively connected to the tag102A,102B and/or base unit110to determine whether a device is responsive and/or ready to execute additional process(es) and/or facilitate function(s). As described above, a program counter of a processor may be in any number of locations during program execution. In some examples, the program counter may be in a location that allows the device (e.g., the tag102A,102B) to be responsive to processing request(s), while in other examples the program counter may be in a location that requires a number of clock cycles before additional processing request(s) can be serviced. For example, if the tag102A receives an RF ACK packet from the base unit, the program counter may be positioned such that audio recording may begin relatively soon after the arrival of the RF ACK packet at one or more pins of the processor202. However, in other examples the receipt of the RF ACK packet by one or more pins of the processor202may not be processed for a greater number of clock cycles because one or more other operation(s) are being processed by the processor202. Such uncertainty regarding when the tag102A is capable and/or otherwise ready to perform frustrates attempts to synchronize actions (e.g., starting a record operation, stopping a record operation, etc.) between the tag102A and other devices. In other examples, the trigger monitor1104may monitor the processor of the tag102A to determine an activity state. Activity states of a processor may be determined by a logical value of a processor pin (e.g., “true,” “false,” “1,” “0,” etc.), which are indicative of a processor that is busy with a current task(s) or available to accept additional task(s).

In operation, the example calibrator1100instructs the tag102A to send an RF packet to the base unit110. The example trigger monitor1104may confirm that one or more portions of the tag102A circuitry (e.g., one or more pins of the processor202) caused the RF packet to be sent. The example trigger monitor1104may also confirm when the example base unit110receives the RF packet by monitoring one or more pins of the base unit110circuitry. When the base unit110receives the RF packet, the example test manager1102may initiate a trigger measurement pulse at a first moment in time. The example base unit110sends an acknowledgement (ACK) RF packet back to the tag102A to inform the tag102A that it is nearby and/or within communication distance. As described above, the RF ACK packet may include payload information to be received and/or processed by the receiving mobile unit, such as the receiving example tag102A. Payload information may include, but is not limited to base unit identification information, time/date information, media identification information, etc.

When the example trigger monitor1104confirms that the tag102A has received the RF ACK packet, the tag102A waits for a delay period (B′). At least one purpose of the delay period B′ is to allow the tag102A to complete processing of the received RF ACK packet before initiating an action, such as an action to begin recording audio. For example, the received RF ACK packet may have a payload of information therein that is parsed by the tag102A. Payload information may include, but is not limited to information related to an identity of the base unit110, time and date information, base unit110operating characteristics, etc. The delay period B′ may be generated by the example delay period adjuster1110and, when B′ expires, the example test manager1102initiates another trigger measurement pulse at a second moment in time. As described in further detail below, the elapsed time between the first moment in time and the second moment in time may be used to adjust the delay period B′.

In the illustrated example ofFIG. 11, the test manager1102determines whether the tag102A is ready to process one or more actions after B′ expires. To determine whether the example tag102A is ready to process one or more actions, the example test manager1102monitors the processor202of the tag102A. In some examples, the test manager1102invokes one or more functions of the processor202to determine whether it can respond to a request immediately, or whether it places the request(s) in a queue/buffer. In other examples, the trigger monitor1104monitors one or more portions of the tag102A circuit (e.g., one or more pins of the processor202) to determine if the processor is finished processing the received RF ACK packet.

If the test manager1102determines that the tag102A is not responsive, or that the tag102A requires additional time before it becomes responsive, then the example delay period adjuster1110increases the value for B′ based on the elapsed time between the first moment in time and the second moment in time. A larger duration for B′ allows, in part, the tag102A to complete its processing of the received RF ACK packet. The example calibrator1100invokes another iteration of testing the tag102A and the base unit110to determine whether or not the larger duration setting for B′ is sufficient based on responsiveness of the tag102A after receiving the RF ACK packet. In other examples, the test manager1102may identify an upper bound value for B′ by increasing a packet length transmitted by the base unit110and received by the example tag102A. When an upper bound value for B′ is identified by the example test manager1102, the value for B′ may be set for all base units and tags to be used in a monitoring environment, such as the example area101of the tag distance calculation system100ofFIG. 1.

The example process1250ofFIG. 12illustrates operation of the test manager1102when calibrating the tags (mobile units) and base units to be used for audience measurement. In the illustrated example ofFIG. 12, operation of the base unit110(left side) and the tag102A (right side) are shown in temporal relation to each other during calibration. The example test manager1102invokes the tag102A that is communicatively connected to the tag interface1106to send an RF packet to the base unit110(block1252), such as an RF initialization packet. The example base unit110is communicatively connected to the base unit interface1108, which is monitored by the example test manager1102to determine whether the base unit110has received the RF packet (block1254). The example test manager1102may employ the trigger monitor1104to monitor base unit110circuitry for an indication that the RF packet was received and/or processed by the base unit110. If the RF packet is not received by the base unit (block1254), the example test manager1102continues to wait, otherwise the test manager1102sends an ACK packet to the tag102, starts a base unit timeout timer, and starts a timer set to a value for the delay period B′ (block1256). If the tag102A does not receive the ACK from the base unit (block1258), then the tag102A waits for receipt of the ACK, otherwise the example tag102A triggers a mobile unit measurement pulse (block1260). As described in further detail below, the mobile unit measurement pulse is used to calculate a delay value between the example tag102A and the example base unit110. The example tag102A also sends an ACK packet back to the base unit (block1262).

If the example base unit110does not receive the ACK packet from the mobile unit prior to expiration of the base unit timeout timer (block1264), then the example process1250restarts. However, if the base unit110receives the ACK packet from the tag102A before the base unit timeout period expires (block1264), then the base unit waits for the delay period B′ to expire (block1266). When the delay period B′ expires (block1266), the base unit triggers a base unit measurement pulse (block1268), and the delay period adjuster1100measures a delay value between the mobile unit measurement pulse and the base unit measurement pulse (block1270).

The example delay period adjuster1110determines whether the value of B′ is too low or too high and, if so, adjusts the value of B′ (block1272). For example, if the value of B′ is too low, then it is possible that the base unit performs one or more actions before the example tag102A is ready to operate. In other words, if B′ is too low, then the base unit110operates prior to the tag102A returning the ACK packet back to the base unit (block1262), which indicates that a larger value of B′ is needed (block1272). As described above, the example tag102A may not be as responsive as the base unit110because, for example, the tag102A processor requires more time to process RF signal(s) received by the base unit110. In other examples, the tag102A processor202may have its program counter in a position such that additional time is required before the processor202can process one or more additional request(s). In such cases where the example tag102A requires additional time to respond, the example delay period adjuster1110adjusts B′ to a larger value and the example process1250restarts. When adjusting B′ to a larger value, the example delay period adjuster1110may increase the value of B′ based on a percentage, a finite incremental value, a predetermined amount of time (e.g., adding 5 milliseconds), etc. Any other manner of determining the increase of the B′ delay value may be implemented, without limitation.

In other examples, the value of B′ may be too large, which causes the example tag102A and the example base unit110to wait unnecessarily. For instance, if the delay between the base unit measurement pulse (block1268) and the mobile unit measurement pulse (block1260) exceeds a threshold value (e.g., 200 milliseconds), then the value of B′ may be reduced by a percentage, a finite incremental value, etc. Determining whether the value of B′ is too large may be accomplished in a number of ways such as, but not limited to, adjusting the value of B′ in an iterative manner until the base unit operates before the example tag102A has an opportunity to transmit its ACK packet back to the base unit (block1262). In such circumstances, the iterative reduction of the value of B′ allows the example delay period adjuster1110to approach and determine a lower level value that should not be crossed. To allow the example tag102A and example base unit110to operate without concern for the value of B′ being too low, the example delay period adjuster1110may use the identified lower level value and multiply it by a safety constant. For instance, if the lower level value of B′ is determined to be 75 milliseconds before the tag102A exhibits an ability to “keep up,” then the example delay period adjuster1110may multiply 75 by a safety constant of 1.5 to establish a value of 112.5 milliseconds for B′.

On the other hand, if the example delay period adjuster1110determines that there is no need to adjust B′ (block1272), then the example tag102A is configured to operate with a tag delay equal to B′ plus the difference between the base unit measurement pulse (block1268) and the mobile unit measurement pulse (block1260) (block1276). In effect, the delay value B′ is initiated by the example base unit110during operation and allows the tag102A to “catch up” before triggering an action when B′ expires.

FIG. 13includes an example audio waveform1302A received by the example tag102A and the same audio waveform1302B received by the example base unit110to illustrate operation of the tag102A and base unit110in a monitoring environment after one or more calibration process(es)1250have occurred. The example audio waveform1302A,1302B is, for example, a portion of audio emitted by a speaker located near the example base unit110. As described above, the example tag102A and the example base unit110have been set with a delay period value B′ for use during operation in a monitoring environment. In the illustrated example ofFIG. 13, the tag102A transmits an RF initialization packet at time t01304in an effort to determine if any base units are nearby. The base unit110receives the RF initialization packet at time t01306because, for all practical purposes, the propagation speed of the RF initialization packet from the tag102A to the base unit110is instantaneous. Similar to the example audio waveform1002A,1002B ofFIG. 10, because the example base unit110is located next to the source of audio, the waveform is shifted, which is represented by time markers (e.g., t0, t1, t2, etc.) of the waveform1302B appearing farther to the right when compared to the time markers of the waveform1302A. To let the tag know that the base unit is within communication range, the base unit110transmits an RF ACK packet at time t41308, after waiting for a random amount of time Bt(1310). The random amount of time Btmay be implemented to minimize the occurrence of crosstalk and/or communication interference when more than one tag and/or base unit are proximate to each other. The ACK packet (at time t4) is received by the tag at time t41312, at which point both the tag102A and the base unit110wait for the previously calibrated delay time B′1314.

As described above, the delay time B′ is selected and/or otherwise calculated to, in part, allow the example tag102A to complete its processing of the received RF ACK packet prior to initiating an action, such as beginning to record audio information in the monitored area (e.g., the example area101ofFIG. 1). In other words, rather than attempt to force the example tag102A to immediately begin collecting audio data after receiving the RF ACK packet (1312), which may not be possible because the tag102A is still processing the received ACK packet, the tag102A and the base unit110both wait for B′ to expire. As such, the example tag102A and the example base unit110may begin a corresponding action at the same time t6(1316).

In the illustrated example ofFIG. 13, the delay time B′1314expires at time t6for both the tag102A and the base unit110. When the example tag102A determines that collection of audio, A1, is complete at time t11, it transmits a stop RF packet to the base unit110. The example base unit110receives the stop RF packet at time t11and marks t11as the time to stop collecting audio (or any other action). Accordingly, both the example tag102A and the example base unit110collect audio data for periods A1and A2, respectively. In other words, time period A1of the example tag102A occurs between time t6and t11, and time period A2of the example base unit110occurs between time t6and t11. Unlike the example tag102A and the example base unit110ofFIG. 10, in which periods A1and A2were not equal and did not start at the same time, the periods A1and A2ofFIG. 13collect audio information for the same duration of time and start at the same moment in time. At least one benefit of facilitating equal action times between the base unit110and the tag102A is that a cursory/preliminary matching may occur without detailed analysis of the contents of the collected data samples saved to memories of the base unit110and/or tag102A. For example, prior techniques to identify a match between tag102A data samples with base unit110data samples included the use of a real time clock (RTC) on the tag102A to time and date stamp each collected sample. To identify a match between the base unit110and the tag102A, the base unit or other evaluation equipment was required to parse the data samples to search for matching time stamp information created by the RTC of the tag102A. However, the methods, systems, articles of manufacture and apparatus described herein allow a match to occur between the collected data samples of the base unit110and tag102A based on an envelope duration of the collected data samples, thereby avoiding additional processing resources required to examine and/or otherwise process the contents of the collected data samples.

The example process1400ofFIG. 14illustrates operation of a mobile unit, such as the example tag102A after it has been calibrated with one or more base units, such as the example base unit110. In the illustrated example ofFIG. 14, the processor202invokes the RF transmitter210to transmit an RF initialization packet on a periodic, aperiodic, scheduled and/or manual basis (block1402). In response to transmitting the RF initialization packet, the RF transmitter210, which may operate as a transceiver capable of both RF transmission and reception, waits for receipt of an acknowledgement (ACK) packet from a base unit110in communication proximity to the tag102A (block1404). If no RF ACK packet is received (block1404), the example timer/counter206determines whether a time out period has expired (block1406). If the time out period has not expired (block1406), then the RF transmitter210, as monitored by the processor202, continues to monitor for the RF ACK packet (block1404). However, if the time out period expires (block1406), then the tag102A may not be within communication distance of one or more base units and the example process1400returns to block1402.

In the event that the RF ACK packet is received (block1404), then the timer/counter206determines whether the delay calculated during the calibration (seeFIG. 12) has expired (block1408). As described above, the calibrated delay is based on the value of B′ plus the amount of time between the mobile unit measurement pulse (block1260) and the base unit measurement pulse (block1268). The example tag102A waits until the delay period B′ expires and, when it does (block1408), one or more actions begin (block1410). As described above, the delay period B′ for the example tag102A is calibrated to be the same as the delay period B′ for the base unit110, both of which are initiated by the transmission/receipt of the RF ACK packet. Accordingly, the base unit110is also performing its corresponding action at the same start time. When the example tag102A determines it is time to stop the action (block1412), the processor202stops the action (e.g., collection of audio in the monitored environment) and transmits an RF stop packet (block1414). The processor202stores any collected data in the memory204(block1416) and the example process1400returns to block1402. In some examples, the processor202causes the collected data stored in the memory204to be transmitted with the RF stop packet, shortly thereafter, or before the next instance where the tag102A collects audio. As such, memory storage requirements of the example tag102A are reduced and, in some examples, the memory204used by the tag102A may be less expensive.

To allow collected data samples of one tag (e.g., tag102A) to be distinguished from collected data samples of another tag (e.g., tag102B), each tag may be configured to perform its action for a period of time that differs from all other tags. For example, tag102A may perform an action (e.g., collecting audio data) for 2000 milliseconds, while tag102B may perform its action for 2020 milliseconds. The base unit110that collects two instances of data samples can associate a match between such collected data samples based on matching the action duration, thereby avoiding resource intensive signal processing activities.

The example process1500ofFIG. 15Aillustrates operation of a base unit, such as the example base unit110after it has been calibrated to employ a delay time B′ with one or more mobile units, such as the example tag102A. In the illustrated example ofFIG. 15A, the processor302invokes the RF interface308to determine whether an RF initialization packet has been received (block1502). If no RF initialization packet is received, the example process1500continues to wait (block1502), otherwise the example processor302determines whether a random waiting period is complete (block1504). As described above, the random waiting period may minimize the crosstalk and/or communication interruption(s) when more than one tag and/or base unit attempts to communicate in a monitored area.

When the random waiting period expires (block1504), the example processor302invokes the RF interface308to transmit an RF ACK packet (block1506), which triggers the beginning of the delay period B′ established by the prior calibration. When the example processor302determines that the delay period B′ has expired (block1508), the processor302invokes the action (block1510). As described above, the example action may include, but is not limited to initiating an audio data collection of a monitored area of interest. The example processor302collects a predetermined quantity of data before stopping the action and storing collected audio data to a memory as data samples (block1514). In some examples, the example processor may monitor the example RF interface308for receipt of an RF stop packet, which may be transmitted by a mobile device, such as the tag102A, to signal an end to the action. As described above, each mobile device may be configured to perform an action for an amount of time that is different from any other mobile device to facilitate matching between collected data samples of the mobile device(s) and base unit. For example, if the base unit detects (and saves) a first set of audio samples for 2000 milliseconds and a second set of audio samples for 2020 milliseconds, and receives a first RF transmission of data samples having a duration of 2000 milliseconds and a second RF transmission of data samples having a duration of 2020 milliseconds, then the base unit110may identify similar or identical durations as matching. When the RF stop packet is received (block1512), the example processor302of the base unit110causes the action to stop and stores any saved data to the memory304(block1514). If the example base unit110is not ready and/or otherwise configured to perform a matching process between collected data samples and data samples received from tag(s) via RF transmission(s) (block1516), then control returns to block1502. However, if the example base unit110is to perform the matching process (block1516), then a matching process is initiated (block1518).

The example process1518ofFIG. 15Billustrates a matching process performed by the base unit110after receiving one or more RF transmissions of data samples from one or more tags. In the illustrated example ofFIG. 15B, the base unit110receives an RF transmission containing data samples from a tag or retrieves previously received data samples from the tag (block1550). During operation, the example base unit110may operate for a period of time while collecting and storing audio samples, and receiving RF transmissions of data samples from one or more tags in one or more example areas, such as the example area101ofFIG. 1. As such, the example base unit110may have one or more sets of data samples received from tags stored in the memory304and one or more sets of data samples stored from the base unit's110storage of audio samples. Each tag operating in the example area101, such as the example tags102A and102B, may be configured to perform its action (e.g., recording audio samples) for a predetermined amount of time. When each tag performs its action for a predetermined amount of time that differs from any other tag, the base unit110may more easily match its collected data samples with a corresponding set of data samples from a tag having the same duration (e.g., 2000 milliseconds).

The example base unit110determines whether the tag data sample duration is equal to a base unit data sample duration that is stored in the base unit110memory304(block1552). If both the base unit data sample duration is equal to the duration of the tag data sample duration (e.g., both are 2000 milliseconds in duration), then the base unit110flags each of the data sample sets as a candidate match (block1554). By examining a data sample duration rather than one or more computationally intensive examinations of the contents of the data sample sets, the base unit110may make a preliminary match between collected tag data and collected base unit data. One or more subsequent detailed data sample analysis procedure(s) may occur to identify other aspects of the collected data samples (e.g., content identification, distance calculation between base unit and tag, etc.), as described above. However, the preliminary match by the base unit110reduces processing requirements of such subsequent detailed analysis procedure(s).

The example base unit110determines whether one or more additional base unit data sample sets are stored in the memory304and, if so, control returns to block1552. On the other hand, if the base unit110memory304has no additional data sample sets, the example process1518ends.

In the illustrated example ofFIG. 16, a message diagram1600includes the first tag102A, the second tag102B and the base unit110. In operation, the first tag102A is configured to perform its action (e.g., recording audio samples and store them to memory204as data samples) for 2000 milliseconds. However, the second tag102B is configured to perform its action for 2020 milliseconds. The example durations of 2000 milliseconds and 2020 milliseconds are described here for purposes of explanation and not limitation. Any other duration may be employed with the example methods, apparatus, articles of manufacture and systems described herein.

The example first tag102A sends an RF initialization packet1602to the example base unit110to determine whether the base unit is within range of the first tag102A. As described above, if the first tag102A does not receive an RF ACK packet within a threshold period of time, the tag102A assumes that it is not near any base units and waits to transmit another RF initialization packet at another time. However, in the event that the base unit110receives the RF initialization packet1602, the base unit110responds with an RF ACK packet1604and begins to wait for the calibrated delay period B′ (1606), as described above. Additionally, upon receipt of the RF ACK packet1604, the example first tag102A begins its calibrated delay period B′ (1608). When the calibrated delay period B′ (1606,1608) expires, the example first tag102A performs its action A1for a period of 2000 milliseconds (1610). At the end of the action A1, the example first tag102A transmits an RF stop packet1612, which causes the example base unit110to also stop its action A2(1614).

The illustrated example ofFIG. 16also includes the second tag102B sending an RF initialization packet1616to the example base unit110, and receiving an RF ACK packet1618. The transmission of the RF ACK packet1618causes the example base unit110to begin a calibrated delay period B′ (1620) and, when received by the example second tag102B, begins the calibrated delay period B′ at the second tag102B (1622). When the calibrated delay period B′ (1620,1622) expires, the example second tag102B performs its action A3for a period of 2020 milliseconds (1624), which is 20 milliseconds greater than the duration of the action of the first example tag102A. At the end of the action A3, the example second tag102B transmits an RF stop packet1626, which causes the example base unit110to also stop its action A4(1628).

The example first tag102A and/or the example second tag102B may store collected audio samples as data samples for a period of time before transmitting the collected data samples via an RF transmission. In some examples, the tags102A,102B store data samples until a threshold amount of memory is consumed, and then transmit the data samples to a base unit to create more available memory storage space. In the illustrated example ofFIG. 16, the first tag102A transmits data samples associated with action A1via an RF packet (1630), and the second tag102B transmits data samples associated with action A3via an RF packet (1632). As described above, the example matching process1518allows the base unit110to match data samples associated with A2and A4with corresponding data samples associated with the first tag102A and the second tag102B, respectively.

FIG. 17is a schematic diagram of an example processor platform P100that may be used and/or programmed to implement any or all of the example tag distance calculation system100, the example tags102A,102B, the example media delivery center106, the example base unit110, the example central facility112, the example server116, the example database118, the example processor202, the example memory204, the example timer/counter206, the example audio sensor208, the example RF transmitter210, the example processor302, the example memory304, the example sensors/transducers306, the example RF interface308, the example ultrasonic transceiver310, the example optical sensor/transmitter312, the example correlation engine318, the example audio transducer314, the example test manager1102, the example trigger monitor1104, the example tag interface1106, the example base unit interface1108and/or the example delay period adjustor ofFIGS. 1-3and11. For example, the processor platform P100can be implemented by one or more general-purpose processors, processor cores, microcontrollers, etc.

The processor platform P100of the example ofFIG. 17includes at least one general-purpose programmable processor P105. The processor P105executes coded instructions P110and/or P112present in main memory of the processor P100(for example, within a RAM P115and/or a ROM P120). The processor P105may be any type of processing unit, such as a processor core, a processor and/or a microcontroller. The processor P105may execute, among other things, the example processes ofFIGS. 5-7A,9,12,14,15A and15B to implement the example methods and apparatus described herein.

The processor P105is in communication with the main memory (including a ROM P120and/or the RAM P115) via a bus P125. The RAM P115may be implemented by dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), and/or any other type of RAM device, and ROM may be implemented by flash memory and/or any other desired type of memory device. Access to the memory P115and the memory P120may be controlled by a memory controller (not shown).

The processor platform P100also includes an interface circuit P130. The interface circuit P130may be implemented by any type of interface standard, such as an external memory interface, serial port, general-purpose input/output, etc. One or more input devices P135and one or more output devices P140are connected to the interface circuit P130.