System and method for converting passive protectors to ANR headphones or communication headsets

A system and method for converting a passive protector earmuff to a communication and/or active noise reduction (ANR) headset include mounting active components to a frame subassembly configured for insertion into the passive earcup to divide the earcup volume into a front cavity without additional passive leak paths and a back cavity having a volume that improves speaker/driver power efficiency with a resistive vent to atmosphere. An earcup having an external shell includes a frame configured for positioning within the external shell and having a first support adapted to contact an interior of the shell and a second circumferential support cooperating with a seal to contact an ear seal plate of the earcup to form the front and back cavities. The frame may support a speaker between the front and back cavity, and secure circuitry within the back cavity.

TECHNICAL FIELD

This disclosure relates to a system and method for converting passive ear muff protectors to an over-the-ear headset or headphones that may include active and passive noise reduction and audio communication technology.

BACKGROUND

Passive hearing protection may include two earcups or muffs joined by a headband and worn over ears of users to enhance or protect hearing. Active and passive attenuation may be provided to protect hearing, reduce loudness of ambient noise, and improve user hearing of desired sounds. Both active and passive attenuation vary as a function of frequency. Various strategies have been developed to provide desired attenuation across frequency ranges of interest. Passive attenuation may be improved by reducing noise leak paths into the ear. However, there are design compromises between user comfort and pressure of the earcups to reduce leak paths. As such, performance can vary from person to person based on how well the earcups fit the head of a user. Significant research and development resources have been expended to engineer and design ear muff shapes and select materials that provide desired performance with respect to passive attenuation, weight, and comfort.

SUMMARY

In various embodiments, a modular insert for an ear muff having an external shell includes a frame configured for positioning within the external shell and having a first support adapted to contact an interior of the external shell and a second circumferential support cooperating with a seal to contact an ear seal plate of the ear muff to define a back cavity between the interior of the shell and the frame and a front cavity between the frame and a user's head. The frame may include an aperture configured to receive a speaker supported by the frame between the front cavity and the back cavity, and supports to secure circuitry coupled to the speaker within the back cavity. The external shell may include or may be modified to include a resistive vent that vents the back cavity to atmosphere.

The modular insert may be used to convert ear muffs to a communication headset which may include a boom microphone. Alternatively, a wired microphone or wireless microphone may be coupled to circuitry on the modular insert. Active noise reduction (ANR) circuitry components may also be provided. For ANR applications, the frame may be configured to support a sense microphone coupled to the circuitry to provide (ANR) operation using the speaker. The resistive vent may include an integrated ambient microphone coupled to the circuitry to provide a feedforward signal for use by the ANR control system. The frame may also be configured to support one or more rechargeable batteries within the back cavity to power the circuitry. The circuitry may include a wired or wireless transceiver to send and receive audio and voice signals using various technologies and protocols, such as Wi-Fi, Bluetooth, Wi-Max, etc.

Embodiments according to the disclosure may provide one or more associated advantages. For example, inserts according to the disclosure leverage previous research and development of ear muffs that provide desirable passive attenuation for conversion to communication headsets or ANR headsets. The components and circuitry for wired or wireless communication or ANR headsets can be mounted to an insertable frame installed within the ear muffs that provides a sealed front cavity to maintain or improve desirable passive attenuation characteristics. Similarly, passive attenuation performance may be maintained by connection of any components that require an external wire or other connection, such as a boom microphone or ambient microphone, through the earmuff external shell into the back cavity. The modular characteristics of the insertable frame may reduce part counts and provide manufacturing flexibility for multiple models of communication and ANR headsets using existing muff/earcup designs and associated existing tooling. Frame shape and positioning may be selected to provide a desired volumetric or other ratio between the back cavity and the front cavity to improve speaker/driver power efficiency and resulting battery life associated with a relatively large back cavity volume. Circuitry installed on the modular frame insert may be tested to assure desired performance prior to assembly within the muffs.

The above advantages and other features and advantages may be recognized by those of ordinary skill in the art based on the following detailed description and accompanying drawings of one or more representative embodiments.

DETAILED DESCRIPTION

FIG. 1is a diagram illustrating a passive ear muff after conversion to a communication headset that may include active noise reduction. System100includes a pair of ear cups102(only one of which is shown) connected by a headband (not shown) or other connecting bridge member that holds ear cups102in position when worn by a user. A headband or bridge member may be positioned over the head, behind the head, under the chin, etc. In various embodiments, the ear cups102are secured to a head protecting safety device such as a helmet or hardhat for example. Each ear cup102includes a shell104having a cushion106around the periphery of a front opening that forms a seal against head108of a user and generally surrounds the pinna of the user's ear110. Depending on the particular application and implementation, shell104may include a membrane or layer112of material selected to provide additional passive attenuation and/or desired structural characteristics for ear cup104. The ear muff may include layer112prior to conversion to a communication headset, or layer112may be installed during the conversion/assembly process. Cushion106may be made of various types of materials that may have an associated compliance characteristic selected for a particular application to reduce or eliminate acoustic leak paths and provide a sealed chamber or cavity120surrounding ear110. For example, cushion106may be manufactured from a viscoelastic material or foam and may include an additional covering or skin (not shown) to enhance durability, comfort, aesthetics, or various other system characteristics.

Prior to conversion according to embodiments of the present disclosure, cavity120is typically the only acoustic chamber or cavity within each shell104and extends from the user's head108to the interior122of shell104. As described in greater detail below, after conversion, cavity120is divided into two separate cavities120,124by an insertable frame130secured within shell104. After frame130is installed, a first cavity120(also referred to as a front chamber or front cavity) extends from the user's head108to frame130, and a second cavity124(also referred to as a back chamber or back cavity) extends from frame130to shell104.

An ear sense reference point or region134may be defined for purposes of design, analysis, and evaluation to be just in front of the opening of ear canal136. For experimental verification of the operation of system100, an ear sense microphone (not shown) may be positioned within ear sense region134, although typically not included in any commercial product. In the illustrated embodiment, ear sense point or region134may be located along the plane140passing through the compression centroid of cushion106and generally concentrically aligned with ear canal136.

In the embodiment illustrated inFIG. 1, insertable frame130includes one or more support arms144a,144bthat support frame130against shell104. In one embodiment, shell104may have depressions or slots molded or machined into interior surface122that cooperate with support arms144a,144b. Similarly, acoustic layer or membrane112may include corresponding holes to accommodate support arms144a,144b. Frame130may also include a circumferential support arm146that cooperates with a gasket or seal148to seal against ear seal plate150and separate front cavity120from back cavity124. This attempts to maintain or minimally affect the passive attenuation characteristics of the passive protector muff by avoiding introduction of additional leak paths associated with conversion of the muff from a passive headset to a communication headset or ANR headphones as described in greater detail herein.

As also illustrated inFIG. 1, frame130may include an aperture configured to receive a speaker152, which may also be referred to as a driver, particularly in ANR headphones and headset applications. Speaker/driver152provides audio output for communication headsets based on communication signals received from a wired and/or wireless connection or communication link. For headphones or headsets having ANR features, frame130may also be configured to receive a sense microphone156. To provide ANR functionality, speaker/driver152receives a combined signal representing audio/communication signals in addition to a noise reduction or noise cancelling signal that is opposite phase and similar amplitude of noise detected by a sense microphone156as generally understood by those of ordinary skill in the art. The noise reduction signal may also be based on input from an ambient microphone158that may be used as a feed forward signal in the ANR control system to further improve ANR performance. In one embodiment, ambient microphone158is integrated within a resistive vent160that provides resistive venting of back cavity124to atmosphere while providing a path for a wired connection between ambient microphone158and corresponding processing circuitry mounted on circuit board170and secured to frame130. The opening for the integrated ambient microphone158and resistive vent160may be molded (and plugged) or machined through shell104during the conversion process.

In various embodiments, ambient microphone158may be separate from any resistive vent160. Positioning of ambient microphone158may vary based on the particular application and availability of existing apertures in shell104. Ambient microphone158should be positioned to minimize any feedback from speaker/driver152. Ambient microphone158may be positioned close to resistive vent160so that a single aperture may be used to reduce sealing requirements and leak paths for noise.

The ambient microphone158may also be used to enhance situational awareness of the wearer by transmitting sounds having predetermined characteristics to speaker/driver152, such as those associated with human speech or a warning siren or horn, for example. The predetermined characteristics may be associated with frequency and/or amplitude of the sounds desired to be transmitted to speaker/driver152, for example.

Circuit board170may include various passive and active, analog and digital, electric and electronic components or modules such as an electrical connector172, a rechargeable (or replaceable) battery174and a microprocessor or microcomputer176to provide various communication and/or ANR processing functions for operation of speaker/driver152, sense microphone156, ambient microphone158, and microphone182(implemented by a boom microphone in the representative embodiment, but generally representing any wired or wireless microphone) depending on the particular application and implementation. Microphone182may be implemented by a comparative digital microphone signal solution, a throat microphone input, or an in-ear microphone that senses pressure differential from jaw movement, for example. Components or modules may include a wireless transceiver to wirelessly receive and transmit audio and voice signals using various technology, such as Bluetooth or Wi-Fi, for example. The particular components or modules may vary depending on the desired features. However, those of ordinary skill in the art will recognize that various components can be assembled and connected on or to circuit board170prior to mounting circuit board170to frame130. During the conversion process, other components mounted to earcup102may be connected via connector172or similar connections to circuit board170prior to inserting and securing frame130within shell104.

To convert the passive protector headset to a communication headset, microphone182may be added. A strain relief connection184may be inserted through a corresponding hole molded (and previously plugged) or machined through shell104during the conversion assembly process. Microphone182may then be electrically connected to circuit board170using connector172. Alternatively, a wireless microphone may be coupled to processor176or similar circuitry via a Bluetooth, Wi-Fi, or other wireless communication link.

As generally illustrated inFIG. 1, the conversion process according to the illustrated embodiment minimizes or eliminates adding any leak paths that may degrade passive attenuation performance by positioning added components that require penetration through shell104within the area of shell104that defines the back cavity124. As such, no additional leak paths are added to front cavity120during the conversion process. Furthermore, selective positioning of frame130within shell104may be used to provide a relatively large back cavity to improve power efficiency of the speaker/driver and resulting battery life. Similarly, the dual cavities created by the sealed frame may improve passive attenuation relative to the single cavity of the passive protector.

Those of ordinary skill in the art will recognize that frame130may be implemented in a variety of different forms consistent with the teachings of the disclosure to provide a modular insert having various components mounted thereto, including processing circuitry and a connector to connect one or more components mounted within earcup102while dividing the initial cavity within shell104into two separate cavities120,124. For example, frame130can be shaped so that circumferential support146and seal148seal against interior surface122of shell104rather than against ear seal plate150. In various embodiments, shell104and/or frame130may be configured for insertion and retention by a helmet, hard hat, or other protective head gear. Similarly, various embodiments may include an unremovable ear seal plate. Frame130may be made of a resilient, flexible material so that it can be easily inserted within the opening formed by cushion106. Alternatively, seal plate150and cushion106may be removed from shell104to facilitate insertion of frame130(and mounted components), and then replaced to secure frame130within shell104. The shape of frame130may vary to provide a desired volumetric or similar ratio between front cavity120and rear cavity124. Power efficiency of speaker/driver152may be improved by forming a relative large back cavity124so that the diaphragm of speaker/driver152may more easily vibrate and return to a neutral position. Resistive vent160may be tuned to balance the power efficiency and acoustic performance of speaker/driver152. For ANR applications, the larger back cavity124and associated resistive vent160may also increase control system headroom.

FIG. 2is a flowchart illustrating a process for converting a passive protector to a communication headset or ANR headphones according to a representative embodiment. Those of ordinary skill in the art will recognize that the order of operations illustrated and described with respect to the flowchart may not necessarily be important to the process or be required to achieve the desired features and advantages. Similarly, all illustrated processes may not be required, and/or omitted processes apparent to those of ordinary skill that may be required may not be illustrated or described for ease of description and illustration. The conversion process may be performed by a manufacturer during initial assembly of the headset or headphones to convert earcups molded for passive protectors for use with communication headsets (which may include a speech microphone, ambient microphone, and/or wirelessly linked components, and may also include ANR features) or ANR headphones (which may not include a speech microphone or ambient microphone). This provides manufacturing flexibility using more common earcups for both passive protectors and active headsets, which may lead to reduced parts inventory, tooling costs, etc. Aftermarket applications may also be possible using a conversion kit.

With reference toFIGS. 1 and 2, process200may begin with subassembly of an insert or frame (130) as represented at202. The particular design of the insert or frame and the selection and subassembly of components may vary depending on the particular model and features provided in the resulting converted product. Subassembly as represented at202may include mounting of a speaker/driver (152) as represented at204, mounting and connection of a sense microphone (160) as represented at206, installation of a battery (174) as represented at208, mounting of a circuit board (170) or similar processing circuitry that may include a microprocessor or microcomputer (176) or other integrated circuits as represented at210, etc. The subassembly may be tuned, calibrated, and/or tested for desired performance as represented at212.

The conversion process may continue with modification of the shell (104) of the earcup (102) as represented at220. Particular modifications will vary based on the selected features and whether the passive protector earcups being converted include any molded features to facilitate conversion (such as orientation/retention slots or pins, blind holes, or plugged holes, for example). As such, block220may include machining of holes or features within or through the shell (104).

The conversion process continues with installation of any added components within or through the shell (104) as represented at230. This may include installation of a speech microphone (182) as represented at232, a resistive vent (160) as represented at234, and/or an ambient microphone (158) as represented at236, for example. As previously described, an integrated ambient microphone and resistive vent may be used. Alternatively, the ambient microphone and resistive vent may be installed in separate locations. However, use of a common aperture may reduce sealing requirements and minimize leak paths as previously described.

Any components installed at230that use wired connections for signaling and/or power may be connected to the circuit board or other connector mounted to the frame subassembly as represented at240. The frame subassembly is then installed and secured within the earcup as represented at250. This may include positioning of the subassembly through the opening of the ear cushion to secure the frame within the earcup shell. The frame may be secured through tension of the frame or resilient seal, using adhesive, or through any other method depending on whether the frame subassembly is intended to be removable or permanently fixed within the earcup shell. Alternatively, the frame subassembly may be installed within the shell prior to installation of an ear seal plate (150) and cushion (106). The frame subassembly may be retained or held in place by tension from the ear seal plate in some embodiments.