Abstract:
An embodiment of a hearing assistance apparatus for performing a Real Ear Measurement (REM), comprises a hearing assistance device housing, a microphone within the housing, an earhook connected to the housing, and a flexible tube. The house has a first opening for guiding sound into the housing to the microphone. The housing and the connected earhook form an interface, where the earhook has a shape to provide a slot near the interface of the housing and the earhook. The tube guides sound, and has a first end and a second end. The first end of the flexible tube and the slot of the earhook cooperate to retain the first end of the flexible tube in the slot of the earhook and flush with the housing to provide a sound-tight connection with the first opening.

Description:
RELATED APPLICATIONS 
     The present application is a divisional of U.S. patent application Ser. No. 12/102,602, filed Apr. 14, 2008 which claims the benefit of priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 60/912,343, filed Apr. 17, 2007, both of which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     This application relates to hearing assistance devices, and more particularly, to real ear measurement (REM) systems for hearing assistance devices. 
     BACKGROUND 
     Hearing assistance devices are electronic devices that provide signal processing functions such as noise reduction, amplification, and tone control. In many hearing assistance devices these and other functions can be programmed to fit the requirements of individual users. Performance of a user&#39;s hearing assistance device, while the device is in the user&#39;s ear, is difficult to measure. The expense of measurement equipment, the time it takes to make the measurements, and the perceived complexity of the procedure, have all proven to be obstacles to widespread use of such measurements. However, such measurements may enable better programming of a user&#39;s hearing assistance device because each user&#39;s ear is different. There is a need in the art for improved systems to assist in measuring the performance of a hearing assistance device while the device is in the user&#39;s ear. 
     SUMMARY 
     The present subject matter provides apparatus and methods for real ear measurements of hearing assistance devices disposed in the ear of a user. Examples are provided, such as an apparatus including a thin tube for detecting sounds near the user&#39;s ear canal with an occluding portion of the hearing assistance device inserted in the user&#39;s ear. The thin tube includes a coupler for connecting the tube to the hearing assistance device. In other examples, a stretchable band of material is included for blocking ports about the housing of the hearing assistance device such that interference from such ports reaching the thin tube microphone is attenuated so as not to interfere with the measurement. 
     The present subject matter also provides methods of making real ear measurements. An example of the method is provided and includes a first procedure of generating a tonal complex signal, analyzing the signal in the frequency domain, applying gains based on pre-stored coupler response data, synthesizing the signal in the frequency domain, presenting the signal to the user&#39;s ear canal using the receiver of a hearing assistance device, capturing the sound near the user&#39;s ear drum using, for example, a first end of a thin tube, analyzing the signal received from a microphone of the hearing assistance device located near the second end of the thin tube, monitoring the signal against limits related to user comfort and output performance of the receiver, and comparing the captured response with a desired response to derive gains that compensate for the shape and volume of the user&#39;s ear canal. The second portion of the example procedure includes generating a tonal complex signal, applying the gains from the first portion of the procedure, presenting the signal to the user&#39;s ear canal, collecting several samples of the signal near the user&#39;s ear drum, analyzing the signal for a bad sample, collecting a number of good samples and averaging the samples to provide an accurate model of the user&#39;s real ear response. 
     This Summary is an overview of some of the teachings of the present application and is not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details about the present subject matter are found in the detailed description. The scope of the present invention is defined by the appended claims and their equivalents. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates an embodiment of a flexible sound tube according to the present subject matter. 
         FIG. 1B  illustrates an embodiment of a hearing assistance device according to the present subject matter. 
         FIG. 1C  illustrates an assembled real ear measurement system according to an embodiment of the present subject matter. 
         FIG. 2  illustrates an embodiment of a real ear measurement system in place to perform a real ear measurement of an ear of a user. 
         FIG. 3  illustrates a first portion of a method of executing a real ear measurement according to an embodiment of the present subject matter. 
         FIG. 4  illustrates a second portion of a method of executing a real ear measurement according to an embodiment of the present subject matter. 
         FIG. 5  illustrates an embodiment of a behind-the-ear (BTE) hearing assistance device with a microphone port blocked. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description refers to subject matter in the accompanying drawings which show, by way of illustration, specific aspects and embodiments in which the present subject matter may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present subject matter. References to “an”, “one”, or “various” embodiments in this disclosure are not necessarily to the same embodiment, and such references contemplate more than one embodiment. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope is defined only by the appended claims, along with the full scope of legal equivalents to which such claims are entitled. 
       FIG. 1A  illustrates an embodiment of a sound tube  112 . The sound tube  112  includes a flexible tube  100  and a plug  101  at one end for providing a sound tight connection with a target device. In one example, the plug  101  includes a recess  102  around the plug  101  to aid retaining the plug  101  in the receptacle of a target device. The tube  100  is very flexible and allows for insertion into the ear canal along side an earmold. Examples of tube materials include a Dow Corning product, part number Q7-4765, a 60 durometer silicone material. Examples of coupling materials include a Dow Corning product; part number Q74850, a 50 durometer material. The example plug materials can be compressed to insert into a tight fitting receptacle and upon relaxation tend to expand to the shape of the receptacle, therefore, forming a sound tight seal. 
       FIG. 1B  illustrates an embodiment of a hearing assistance device. The illustrated hearing assistance device includes a hearing assistance device housing  103 , a flexible sound tube  112  and an earhook  104 . In the illustrated example, the hearing assistance device housing  103  includes a port  105  for sound emanating from a receiver enclosed in the housing  103 , a first input opening  106  for guiding sound to a microphone, and a second input opening  107  located adjacent a microphone hood  108 . In various embodiments, microphones of various types are disposed within the hearing assistance device for receiving sound, such as, omni-directional microphones, directional microphones or combinations thereof. In some examples, a microphone is associated with each input opening. In some examples, a microphone uses multiple openings to receive sound. 
     In the illustrated example, the earhook  104  accommodates a receiver enclosed in the hearing assistance device housing. In various embodiments, the earhook accommodates wired or wireless receivers located remotely from the hearing assistance device housing. The illustrated earhook of  FIG. 1B  uses a threaded connector  109  to attach to the hearing assistance device housing  103 . In various embodiments, the earhook  104  attaches using a friction fit connector or a twist and lock connector. The illustrated earhook includes a receptacle  110  to accommodate the connection of the flexible sound tube  112 . In the illustrated example of  FIG. 1B , upon connection of the earhook  104  to the hearing assistance electronics housing  103 , the sound tube receptacle  110  of the earhook  104  is aligned with the first microphone port  106  of the housing  103 . 
     The sound tube plug  101  attaches to the earhook  104  using the sound tube receptacle  110 . In the illustrated example, the plug  101  is pressed into the receptacle  110  such that the recess  102  of the plug  101  mates with the raised profile  111  of the receptacle  110 . As the plug  101  presses into the receptacle  110 , the plug material compresses to pass through the restricted opening of the receptacle slot. After the plug  101  fully enters the slot, the plug material relaxes and expands to fill the receptacle  110  thus forming a sound-tight connection. The open portion of the receptacle  110 , allows verification of the connection in that the user can verify the end of the plug is flush with the face of the hearing assistance device housing. The open portion of the receptacle  110  also allows the user to observe the mating of the sound tube plug recess  102  with the corresponding raised profile  111  of the sound tube receptacle  110 . 
       FIG. 1C  illustrates an assembled real ear measurement system according to one embodiment of the present subject matter.  FIG. 1C  includes a hearing assistance device housing  103 , a flexible sound tube  100  with a plug  101  and an earhook  104  according to the present subject matter. The assembled embodiment shows the plug  101  of the sound tube engaged in the receptacle of the earhook  104  attached to the hearing assistance device housing  103 . 
       FIG. 2  illustrates an embodiment of a real ear measurement system in place to perform a real ear measurement of an ear  231  of a user  232 . The illustrated example shows a user  232  wearing a hearing assistance device housing  203  with a connected earhook  204  and flexible tube  200 . The unconnected end of the flexible tube  100  is inserted into the user&#39;s ear canal along side an earmold  230  connected to the earhook  204 . The end of the flexible tube extending into the ear canal should be close to the eardrum, for example, approximately 5 mm from the eardrum, to minimize the collection of bad measurements. In various examples, the thin, flexible tube is connected to housing designs other than the illustrated behind-the-ear design, for example, over-the-ear, on-the-ear and custom housings designs may be employed with the thin, flexible sound tube. During an ear measurement, a calibrated sound is emitted from the receiver of the hearing assistance device. The calibrated sound, as detected in the ear canal, is received by a first microphone of the hearing assistance device using the flexible sound tube. Because the transfer function of the flexible sound tube is easily derived and/or obtained, the hearing assistance electronics digitize a signal representing the actual sound pressure level (SPL) in the ear canal over a desired range of frequencies. 
       FIGS. 3 and 4  demonstrate a first process and a second process useful for ear measurements according to one embodiment of the present subject matter. A patient is given a hearing assistance device fitted with the thin, flexible tube  100  of  FIG. 1C , the thin, flexible tube connected to the earhook  104  and proximate the sound tube microphone opening  106 . Prior to providing the hearing assistance device, a coupler response of the hearing assistance device conducted at the factory is stored in the memory of the hearing assistance device for use as a reference for subsequent measurements of the user&#39;s ear canal. Additionally, data relating to the coupler response of the hearing assistance device over a broad range of parameter settings, or the electro-acoustical behavior of the hearing assistance device, is also stored in the memory of the hearing assistance device. 
     In some embodiments, the hearing assistance device is in communication with a programmer. The programmer sends a command to initiate a fitting procedure. In other embodiments, a programmer is not connected and the fitting procedure is initiated using the controls of the hearing assistance device. In examples where the hearing assistance device has multiple microphones, only the sound tube microphone is active for the fitting procedure. In examples where the hearing assistance device has multiple input sound openings, some openings are occluded to minimize reception anomalies of the active microphone resulting from multiple sound paths. A microphone opening may be occluded as in  FIG. 5  to improve the quality of measurements from the sound tube microphone. 
     In various examples, a periodic signal  350  is injected into the device during the fitting procedure, converted into the frequency domain by analysis block  351  and amplified  352  by gains  359  calculated to achieve a desired level  358 . In other examples, the fitting procedure advances using the hearing assistance device generate the periodic signal. Varying tones of different frequencies are used as the periodic signal  350 . These tones are selected to assist in providing a sinusoidal signal of interest to map the transfer function of the listener&#39;s actual inner ear canal with the hearing aid in position. In various embodiments, tones are selected at 100 Hertz intervals. The uncomfortable level (UCL) and receiver saturation  357  are monitored to assure the receiver transmits the signal at a level comfortable to the user and within the linear operating of the receiver. In various embodiments, UCL parameters are pre-stored in the hearing assistance electronics and are customized to the user. The resulting amplified tones are converted back into the time domain by synthesis block  353  and played to the receiver  354 . The tones played by receiver  354  are picked up by the sound tube in the ear canal and received by the sound tube microphone  355 . The gain of the system is thus adjusted to the desired levels for frequency regions of interest. 
     After the gains are established, the system can perform the process of  FIG. 4 . In various embodiments, periodic signals of interest  450  are injected into the hearing aid signal channel. In some examples, the hearing assistance device generates and injects the periodic signals of interest  450 . The signal is then converted into frequency domain by the analysis block  451  and amplified as a function of frequency  452  with gains as provided by the prior process  459 . The conversion of the signal to the frequency domain in blocks  451  and  456  of  FIG. 4  and blocks  351  and  356  of  FIG. 3  is achieved by transforms well known in the art, for example, a filter bank, FFT or other transformation to convert the signal from the time domain into the frequency domain. The resulting amplified signals are converted into the time domain by synthesis block  453  and played by receiver  454 . The sound tube microphone receives the sound  455  near the eardrum and the received sound is converted into a frequency domain signal at analysis block  456 . The system then looks at temporal variations in the microphone response while in the frequency domain to determine if momentary interferences (or bad capture)  461  and/or body movements  462  are present. Such samples are rejected and only “clean” samples are used to generate a more accurate running average  463  of the microphone response. To minimize the effects of captured anomalies several samples are collected. In various embodiments, up to 500 samples are collected. Embodiments with more memory collect more than 500 samples. In one embodiment, microphone signal capture is randomly triggered  460  to increase resistance to periodic interference, such as talking or coughing during measurement 
     The process is repeated several times for each desired frequency such that a statistically accurate representation of the user&#39;s real ear response is obtained using the stored data. The use of periodic sinusoidal tones allows the processes to provide a shorter analysis and determination of real ear response as compared to analysis of random or white noise stimuli. In various embodiments, the analysis and capture of samples of real ear measurements is completed in 2.5 to 5 seconds depending on the number of rejected samples, the total samples collected and transducer sensitivity. The use of periodic, sinusoidal tones also provides resistance to biases introduced to the saved data by background noise. 
     After the fitting procedure measures the response of the user&#39;s ear, the response is processed with the pre-stored coupler response to produce the real-ear coupler difference (RECD). The RECD is stored in the memory of the hearing assistance device. The thin tube is removed as the RECD and the stored electro acoustical behavior of the hearing assistance device is used to provide accurate data of the actual response of the user&#39;s ear. A programmer in communication with the hearing assistance device can display data received from the hearing assistance device. Such data accurately indicates the input to and the output of the actual hearing assistance device while in the ear of the actual user, instead of an approximation based on average RECDs and average coupler responses. Such information can be used to provide additional diagnoses and/or treatment of the user. 
       FIG. 5  illustrates an example of a behind-the-ear hearing assistance device  520  with a microphone port blocked to minimize interference with a real-ear measurement. The illustrated hearing assistance device includes a band of stretchable material  512  positioned about the housing  503 . The device is shown with the band  512  in a position such that a second microphone port located under the protruding microphone hood  508  is occluded by the placement of the stretchable band of material  512  over the port opening. The band is manually positioned and can be removed or slid to a different location than illustrated to allow sound to access the port. In various embodiments, a port is occluded with a plug inserted in to the port opening. 
     This application is intended to cover adaptations or variations of the present subject matter. It is to be understood that the above description is intended to be illustrative, and not restrictive. The scope of the present subject matter should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.