Patent Publication Number: US-2021195336-A1

Title: Aircraft Stereo Headset for 3D Audio Using Four-Wire Plug

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to stereophonic sound reproduction in aircraft, and in particular, it concerns transmission of stereo audio and microphone signals using a standard legacy four-wire plug connection. 
     BACKGROUND OF THE INVENTION 
     Referring now to  FIG. 1 , a schematic diagram of a conventional, current standard military pilot headset plug  104 . Four conductors are used, known as a four-wire plug. Two conductors, speaker positive ( 102 P, SPK+) and speaker negative ( 102 N, SPK−), are used to transfer monaural (mono) sound. In monaural (mono) sound one single audio channel is used. The mono audio can be reproduced through more than one speaker, but all speakers are still reproducing the same copy of the single audio signal. A standard military pilot headset has two speakers, referred to as earphones. 
     The headset plug  104  also includes two other conductors, microphone positive ( 100 P, MIC+) and microphone negative ( 100 N, MIC−), that are used to transmit the pilot&#39;s voice from the microphone. In fighter aircraft a conventional low impedance dynamic microphone located inside the pilot&#39;s oxygen mask is utilized. 
     SUMMARY 
     A system for transferring stereo audio required for 3D audio presentation to pilots, allows a legacy four conductor headset plug to carry at least five signals. At least five signals are needed to support stereo audio and microphone, in place of mono audio presented to the pilot and microphone. The headset microphone negative and speaker-left negative lines are connected, preferably only at the headset plug and jack. A low-to-high impedance microphone amplifier is employed on the microphone line, and high impedance earphones are used. This combination reduces unwanted crosstalk between the speaker and the microphone signals to acceptable levels, while providing stereo audio to a user. Replacement of a four-conductor headset plug with a headset plug containing more conductors is problematic, as a change of the headset plug would require expensive ejection seat re-testing. 
     According to the teachings of the present embodiment there is provided a military flight audio system including: high impedance earphones including a first speaker and a second speaker, a low impedance microphone, an amplifier operationally connected to the low impedance microphone, and an audio plug having first, second, third, and fourth conductors, wherein: the first conductor is coupled to a first input of the first speaker, the second conductor coupled to a first input of the second speaker, the fourth conductor coupled to a first output of the amplifier, and the third conductor coupled to a second input of the first speaker, a second input of the second speaker, and a second output of the amplifier. 
     In an optional embodiment, the third conductor is coupled by connecting the second input of the first speaker, the second input of the second speaker, and the second output of the amplifier at a location internal to the audio plug. 
     In another optional embodiment, the high impedance earphones have an impedance on the order of 150 ohm and an output of the amplifier has an impedance on the order of 300 ohm. 
     In another optional embodiment, the first speaker is a left stereo headset earphone and the second speaker is an associated right stereo headset cup. 
     In another optional embodiment, the audio plug is selected from the group consisting of: a military pilot headset plug, and an Amphenol U-92 A/U plug. 
     In another optional embodiment, the first conductor is a speaker positive connection, the second conductor is a speaker negative connection, the third conductor is a microphone negative connection, and the fourth conductor is microphone positive connection. 
     In another optional embodiment, further including an audio jack coupling the audio plug to an audio management module, the audio jack selected from the group consisting of: a military pilot headset plug, and an Amphenol U-93 A/U jack. In another optional embodiment, the audio jack has fifth, sixth, seventh, and eighth conductors, the fifth conductor coupled to the first conductor and configured for a first audio signal, the sixth conductor coupled to the second conductor and configured for a second audio signal, the eighth conductor coupled to the fourth conductor and configured for a fourth audio signal, and the seventh conductor coupled to the third conductor and configured for a third audio signal. In another optional embodiment, the first audio signal is a left stereo positive signal, the second audio signal is a right stereo positive signal associated with the left stereo positive signal, the fourth audio signal is a microphone positive signal, and the third audio signal is a common ground. 
     In another optional embodiment, the amplifier has an amplification selected from the group consisting of: on the order of 40 dB, on the order of 50 dB, and on the order of 60 dB. 
     In another optional embodiment, the first and second speakers include noise reduction modules. In another optional embodiment, the noise reduction modules are active noise reduction (ANR) modules and the first and third conductors and the second and third conductors each pair provide phantom power to the active noise reduction modules. 
     In another optional embodiment, the third conductor and the fourth conductor provide phantom power to the microphone amplifier. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES 
       The embodiment is herein described, by way of example only, with reference to the accompanying drawings, wherein: 
         FIG. 1  is a schematic diagram of a conventional military pilot headset plug. 
         FIG. 2  is a schematic wiring diagram of conventional mono audio military pilot headset and plug. 
         FIG. 3  is a schematic diagram of an exemplary embodiment of a system implementing stereo audio with a legacy military pilot headset and plug according to the invention. 
     
    
    
     DETAILED DESCRIPTION—FIRST EMBODIMENT—FIG.  1  TO FIG.  3   
     The principles and operation of the system according to a present embodiment may be better understood with reference to the drawings and the accompanying description. A present invention is a system for transferring stereo audio, that is required for spatial 3D audio, via a legacy conventional, current standard military pilot headset plug, transferring at least five signals via a standard four conductor connection. 
     The system facilitates stereo audio that is required for spatial three-dimensional (3D) audio providing directionality for perceived audio, as compared to current mono audio. 3D audio supports radio separation, hence communication intelligibility, and increased survivability, for example directional audio warning cues from ground missile threats. One example of 3D audio is Orbit&#39;s (Orbit Communications Systems Ltd, Netanya, Israel) 3D Audio technology based on utilizing Head Related Transfer Functions (HRTF) for reproduction of 3D sound in stereo headsets. By providing the pilot with directional audio cues, the spatial direction of the sound source can be perceived. 
     In general, a military flight audio system of the current embodiment ( 290 ) includes: high impedance earphones including a first speaker and a second speaker, a low impedance microphone, an amplifier operationally connected to the low impedance microphone, and an audio plug ( 104 ) having first ( 102 P, SPKL+), second ( 102 N, SPKR+), third ( 100 N, SKL−, SPKN−, MIC−), and fourth ( 100 P, MIC+) conductors. The first conductor is coupled to a first input (SPKL+) of the first speaker ( 238 L), the second conductor coupled to a first input (SPKR+) of the second speaker ( 238 R), the fourth conductor coupled to a first output (MIC+) of the amplifier ( 246 P), and the third conductor coupled to a second input (SPKL−) of the first speaker ( 238 L), a second input (SPKR−) of the second speaker ( 238 R), and a second output ( 246 N) of the amplifier ( 246 ). 
     A significant problem in achieving high quality stereo signals in aircraft is the high crosstalk occurring between microphone and earphone channels as a result of limitations of using a conventional four-wire plug connector to transfer five signals. In particular, connection of a speaker negative signal to a microphone negative signal causes unacceptable crosstalk. Audio channel signals are related to a left earphone element, a right earphone element, and a microphone. 
     This crosstalk is a signal leakage from one audio channel to another audio channel. Typically, crosstalk between the microphone channel and mono earphone channel in military aircraft is approximately −40 dB due to conventional wiring methods. In general, separation between the earphone channels and the microphone channel of less than 40 dB is not acceptable. 
     Good crosstalk separation is not difficult to achieve in today&#39;s general audio systems. However, wiring for a headset connection with a four-wire plug used in most aircraft prevents delivering high quality stereo audio to aircrew. At first glance, there seems no problem supplying stereophonic audio to an aircrew member using a common negative wire for the left and right earphones and the microphone. There are adequate wires in a four-wire plug to close all needed electrical circuits. However, upon further examination, the common negative wire will cause unacceptable crosstalk between the microphone and the earphone channels at least in part due to the high electrical current of the earphone channels compared to the lower electrical current of microphone channel. 
     Replacement of a four-conductor headset plug with a five or six-conductor headset plug is problematic, as this implementation would require expensive ejection seat retesting due to the fact that during pilot ejection the headset plug separates from the jack. 
     Typical engineering implementations in a variety of fields to re-use existing conductors, such as the analog audio four-wire plug conductor, for additional capability focus on implementing digital signals via legacy conductors. Digital implementations require the addition of processing (hence hardware, software, and supplied power) to both sides of the conductor, as well as additional hardware on one or more sides for analog-to-digital and digital-to-analog conversion. 
     While the current description uses an example of a military pilot headset and corresponding plug-jack combination, this implementation is not limiting. Implementations can be used for non-military, commercial applications. In addition, implementations can be used for devices other than audio headsets, and applications using additional and/or other configurations of conductors. For example, a four conductor commercial jack configuration from tip to sleeve of respective left, right, ground, and mic signals. 
     An innovative configuration of connections and support hardware modules allows a legacy four conductor military pilot headset plug  104  to carry at least five signals. Additional signals, beyond four, are needed to support stereo audio, in place of the current mono audio presented to the pilot. The current headset plug, jack, and associated hardware for a military pilot headset have undergone extensive ejection seat testing. Upon ejection of the pilot, the headset plug (U-92) must detach from the headset (socket) jack (U-93). Using a different plug and jack to support additional conductors, in place of the current standard plug, would entail expensive ejection seat testing with the different plug and jack hardware. Thus, if the current hardware can be used, acceptance and deployment can be significantly less expensive than using a different hardware connector. 
     A feature of the current embodiment is the use of the existing analog legacy four conductor military pilot headset plug  104  to carry at least five analog signals. Existing, already tested hardware can be used with minimal changes to provide stereo audio to a user (such as a pilot). 
     Operational benefits of spatial 3D audio for pilots include:
         Survivability—Directional Radar Warning Receiver (RWR) cues to ground and air threats, fully synchronized to head-mounted display (HMD) visual cues.   Radio separation—Enhances intelligibility of multiple radio channels.   Locating wingmen—Directional flight formation radio allows locating wingmen in a quicker manner. Especially when formation breaks or during a dogfight.   Safety—Directional Anti-Collision warnings between aircraft flying in formation.   Locating targets—Infra-red (IR) missile tones for locating enemy targets.   Safety—Directional audio alerts increase flight safety, for example: left/right engine alert.       

     Referring now to the drawings,  FIG. 2  is a schematic diagram of a conventional mono (single audio channel) headset  250  with a legacy military pilot headset plug  104 . Elements of the drawings have been drawn for clarity of connections and configuration, not to scale or as the actual devices are built. For example, vertical arrangement on the page of elements of the plug  104  are not in the same order as the order of the physical connections shown in  FIG. 1 . Instead, the elements are arranged for clarity of connections between elements in the figures. For clarity, to assist with understanding the innovative configuration of stereo headset  220 , described below, elements of the current figure are drawn with respect to left and right earphones (speakers). One skilled in the art will realize that the designation of left and right is only for clarity of reference, as the audio in a conventional military plug is monaural. 
     A mono headset  250  includes a left earphone  238 L and a right earphone  238 R, for receiving the single speaker signal. The left earphone  238 L includes a left speaker positive input  238 LP, a left speaker negative input  238 LN Similarly, the right earphone  238 R includes a right speaker positive input  238 RP, a right speaker negative input  238 RN. The left and right earphones ( 238 L,  238 R) are connected in parallel so that the speaker signal is identical to both earphones providing mono audio. Conventional, standard, military low impedance speakers on the order of 19 ohm each, with an impedance of 9.5 ohm as the two mono speakers are connected in parallel. The left and right earphones ( 238 L,  238 R) are non-limiting examples used in the current description for speakers, and more generally for audio output devices. 
     The mono headset  250  also includes a microphone ( 248 , MIC) providing a microphone signal. The microphone  248  includes a microphone positive terminal  248 + and a microphone negative terminal  248 −. The microphone  248  is typically a low impedance, 5 ohm, dynamic microphone located inside the pilot&#39;s oxygen mask, 
     A plug connector  104  is typically a male connector. In the currently exemplary implementation of a military pilot headset, an Amphenol U-92 A/U plug (available from Amphenol Nexus Technologies, Stamford, Conn., USA) can be used. As described above, the plug  104  has four conductive areas that in standard implementations are plug speaker-positive ( 102 P, SPK+), plug speaker-negative ( 102 N, SPK−), plug microphone-positive ( 100 P, MIC+) and plug microphone-negative ( 100 N, MIC−). 
     In a conventional implementation of a mono headset, the plug  104  is connected as follows:
         The plug speaker-positive  102 P to both of the positive speaker inputs (the left speaker positive input  238 LP and the right speaker positive input  238 RP),   the plug speaker-negative  102 N to both of the negative speaker inputs (the left speaker negative input  238 LN the right speaker negative input  238 RN),   the plug microphone-positive  100 P to the microphone positive  248 +, and   the plug microphone-negative  100 N to the microphone negative  248 −.       

     Corresponding to the plug  104  connector is a jack  206  connector. Typically, the jack  206  connector is a female connector, also known in the field as a “socket”. In the currently exemplary implementation of a military pilot headset, an Amphenol U-93 A/U jack can be used. The jack  206  has four conductive areas that in standard implementations are jack speaker positive  202 P, jack speaker negative  202 N, jack microphone positive  200 P, and jack microphone negative  200 N. 
     When the plug  104  connector is inserted into the jack  206  connector, the conductors of the plug  104  contact the conductors of the jack  206 , as is known in the field:
         the plug speaker-positive  102 P, to the jack speaker-positive  202 P,   the plug speaker-negative  102 N, to the jack speaker-negative  202 N,   the plug microphone-negative  100 N to the jack microphone-negative  200 N, and   the plug microphone-positive  100 P to the jack microphone-positive  200 P.       

     Referring now to the drawings, FIG. is a schematic diagram of an exemplary embodiment of a system  290  implementing stereo audio with a legacy military pilot headset plug  104  and jack  206 . Elements of the drawings have been drawn for clarity of connections and configuration, not to scale or as the actual devices are built. 
     As noted above, the elements of the conventional mono headset  250  of  FIG. 2  were laid out for clarity to correspond to the innovative configuration of elements, hardware, and connections of the current figure&#39;s stereo headset  220 , described below. 
     A stereo headset  220  includes a left earphone  238 L and a right earphone  238 R, each for receiving respective left and right speaker signals. The left earphone  238 L includes a left speaker positive input  238 LP, a left speaker negative input  238 LN, and optionally an active noise reduction (ANR) module left ANRL. Similarly, the right earphone  238 R includes a right speaker positive input  238 RP, a right speaker negative input  238 RN, and optionally an ANR module right ANRR. 
     The stereo headset  220  also includes a low impedance microphone ( 248 , MIC) located inside the pilot&#39;s oxygen mask providing a microphone signal, connected to a microphone amplifier ( 246 , AMP). The amplifier  246  is typically located outside the oxygen mask. The amplifier  246  has microphone positive  246 P and microphone negative  246 N connections for the respective microphone  248  connections (the microphone positive terminal  248 + and the microphone negative terminal  248 −). One skilled in the art will realize that the connections  246 N and  246 P towards the plug  104  represent the microphone signals amplified and with high impedance as seen by connection to the MIC module  216 . 
     An audio input module  247  is defined including the microphone  248  and the amplifier  246 . 
     An audio management system can include generation, control, mixing, signal processing and distribution of one or more audio signals, receiving of microphone inputs, and optional functions such as power management and supply. An exemplary audio management system used in this description is an Orbit audio management system (AMS)  210 . The AMS  210  includes a 3D audio module  214 . The 3D audio module  214  provides functions including signal processing, control, and generation of at least two signals, a stereo signal, for example as follows:
         a left stereo signal positive (SPKL+) on an AMS speaker-left positive line  212 L+ to the jack speaker-positive  202 P,   a right stereo signal positive (SPKR+) on an AMS speaker-right positive line  212 R+ to the jack speaker-negative  202 N,   a left stereo signal negative (SPKL−) on an AMS speaker left negative line  212 L− to the jack microphone-negative  200 N,   a right stereo signal negative (SPKR−) on the AMS speaker right negative line  212 N also to the jack microphone-negative  200 N,   a mic module  216  positive signal (MIC+) on an AMS microphone-positive  210 P line to the jack microphone-positive  200 P, and   a mic module  216  negative signal (MIC−) on an AMS microphone-negative  210 N line also to the jack microphone-negative  200 N.       

     Optionally, module  214  also provides phantom power between the speaker-negative line  212 N and the speaker-left positive line  212 L+, and between the speaker-negative line  212 N and the speaker-right positive line  212 R+, to power the ANR modules (the ANR module left ANRL and the ANR module right ANRR) in the headset. 
     Optionally, the speaker negative line  212 N can be separated to speaker-left negative line  212 L- and speaker-right negative line  212 N in order to achieve higher separation between the left and right speaker signals. 
     The AMS  210  also includes a microphone module  216 . The microphone module  216  can provide phantom power between the microphone positive line ( 210 P, MIC+) and the microphone negative line ( 210 N, MIC−), to power the microphone amplifier  246 . 
     A configuration of connections and support hardware modules allows a legacy four conductor plug  104  to carry at least five or six signals is as follows:
         The left speaker positive input  238 LP is connected via a headset speaker-left positive line  232 L+ (SPKL+) to the plug  104  speaker-positive  102 P conductor.   The right speaker positive input  238 RP is connected via a headset speaker-right positive line  232 R+ (SPKR+) to the plug  104  conductor  102 N.   The left speaker negative  238 LN is connected via a headset speaker-left negative line  232 L− (SPKL−) also to the plug  104  microphone-negative  100 N conductor.   The right speaker negative  238 RN is connected via a headset speaker-right negative line  232 N (SPKR−) also to the plug  104  microphone-negative  100 N conductor.       

     From the microphone amplifier  246 , the microphone negative  246 N connection is via a microphone-negative line  240 N (MIC−) also to the plug  104  microphone-negative  100 N conductor, and the microphone positive  246 P connection is via a microphone-positive line  240 P (MIC+) to the plug  104  microphone-positive  100 P conductor. 
     In an alternative configuration, instead of the above-described six signals ( 212 L+,  212 R+,  212 L−,  212 N,  210 N,  210 P), transferring stereo audio via a legacy conventional four conductor connection can be implemented using five signals on the jack side, by eliminating the AMS speaker-left negative line  212 L−, as the left speaker negative  238 LN is connected via the headset speaker-left negative line  232 L− to the plug  104  microphone-negative  100 N conductor. Thus, reusing the common negative connection of the plug microphone-negative  100 N and the jack microphone-negative  200 N. Although the five-signal implementation may have more crosstalk between the left and right speaker channels, as compared to the six-signal implementation (thus reducing the stereo effect because of a reduction in the separation of left/right channels), operation of the five-signal implementation of the current embodiment can still be within an acceptable level of separation. Combining (five signals) or separating (six signals) implementation is dependent on the desired implementation and operation. 
     In the current exemplary embodiment of providing stereo to a headset, six signals are shown being transferred via four conductors (four conductor plug). The signals can generally be referred to as:
         MIC− (microphone negative)   MIC+ (microphone positive)   SPKL+ (speaker left positive)   SPKR+ (speaker right positive)   SPKL− (speaker left negative)   SPKN− (speaker right negative) The designator “SPKN−” is used instead of “SPKR−” as this is used as a common negative in both the six-signal and five-signal implementations.)       

     On the plug side, the MIC− (microphone-negative line  240 N), SPKN− (headset speaker-right negative line  232 N) and SPKL− (headset speaker-left negative line  232 L−) are connected to same conductor (microphone negative  100 N), thus no plug change is required. This configuration saves the cost of ejection seat retesting (saving significant expense per aircraft type). Correspondingly, on the jack side, the MIC− (AMS microphone-negative  210 N), SPKR− (AMS speaker-negative line  212 N), and SPKL− (AMS speaker left negative line  212 L) lines are connected to the same conductor (jack microphone-negative  200 N). 
     Normally, such connecting (of MIC− and SPKN− lines to the same plug conductor  100 N) causes unacceptable crosstalk between microphone and speaker signals. In particular, crosstalk separation of at least 40 dB is desired (required) between the microphone and speaker signals, which is not achieved when these lines are simply connected. 
     In order to overcome this problem and achieve acceptable crosstalk between the microphone and speaker signals, the following features can be implemented: 
     1) Connection of the MIC− (microphone-negative line  240 N), the SPKN− (headset speaker-right negative line  232 N), and the SPKL− (headset speaker left negative line  232 L) is done preferably only within the plug  104  and correspondingly only within the jack  206  (within  100 N and  200 N in the current figure). In general, the further away from the entrance to the plug  104  and entrance to the jack  206  (further away from the plug microphone negative  100 N conductor) the connection is implemented, the more crosstalk there will be between the microphone and speaker signals. The maximum distance the connection can be from the entrance conductor depends on the acceptable level of crosstalk allowed. 
     2) Use of a low-to-high impedance amplifier (amp  246 ) on the microphone line between the mic  248  and the plug  104 . In the context of this document, the term “low-impedance” for the microphone refers to impedance of 5 ohm, or on the order of 5 ohm. In the context of this document, the term “high-impedance” for the microphone refers to typical impedances of 150 ohm or higher. The amplification is typically greater than 50 dB, preferably on the order of 60 dB. The terms “high impedance” and “low impedance” in reference to the microphone will be understood by one skilled in the art. 
     3) Using high impedance earphone speakers for the left  238 L and right  238 R earphones (in place of standard military low impedance speakers on the order of 19 ohms each, with an impedance of 9.5 ohms as the earphones are connected in parallel). In this context, high impedance for speakers/earphones is typically 150 ohm or above, preferably on the order of 300 or 600 ohm (using standard, available components). The terms “high impedance” and “low impedance” in reference to the earphones will be understood by one skilled in the art. 
     One of the results of the combination of the above three features is reducing current carried in the connected conductor, thereby achieving acceptable signal separation between the microphone and speaker signals. 
     Embodiments can be used with or without active noise reduction (ANR). Different methods of noise reduction can be used to reduce the noise, and are dependent on the application and noise sources in the environment, such as in an aircraft cockpit. Noise reduction methods can include: 
     1. Microphone Noise Reduction—Reducing noise that enters the pilot&#39;s microphone, so that the pilot&#39;s voice without noise is transmitted over the radio (or intercom) for increased intelligibility. ANR can be implemented within the AMS  210 . 
     2. Active Noise Reduction Headphones—Reducing ambient noise reaching the pilot&#39;s ears. Implemented within the headset (not part of the AMS  210 ), shown in the current figure as left ANR module ANRL and right ANR module ANRR. This reduction is relevant for both helicopter and fighter aircraft. Solutions are available off the shelf for transport and civil aviation. 
     3. Electrical Noise Reduction—Reducing electrical noise from aircraft auxiliary systems, for example, induced on the analog audio input lines to the AMS  210  causing the pilot to hear high-pitched tones. This reduction can be especially relevant in fighter aircraft. One option for implementation is to use dedicated filters within the AMS  210  to reduce and/or eliminate this source of noise. 
     According to the teachings of the present embodiment there is provided a system ( 290 ) for conducting multiple analog signals (SPKL+, SPKR+, SPKL−, SPKN, MIC−, MIC+), the system including: an audio plug ( 104 ) having at least one conductor ( 100 N) receiving two or more signal leads ( 232 L,  232 N,  240 N) at a common location ( 100 N), the two or more signal leads being shorted at a given distance from the common location. 
     In an optional embodiment, wherein the given distance is less than a maximum threshold distance which is pre-determined to prevent crosstalk between the two or more signal leads from exceeding a given acceptable crosstalk level. 
     In another optional embodiment, wherein the maximum threshold distance is on the order of 5 centimeters and the given acceptable crosstalk level is 30 dB. 
     In another optional embodiment,
         (a) the audio plug ( 104 ) has first ( 102 P, SPKL+), second ( 102 N, SPKR+), third ( 100 N, SKL−, SPKN−, MIC−), and fourth ( 100 P, MIC+) conductors,   (b) the first conductor coupled to a first input (SPKL+) of a first speaker ( 238 L),   (c) the second conductor coupled to a first input (SPKR+) of a second speaker ( 238 R),   (d) the fourth conductor coupled to a first output (MIC+) of an audio input module (MIC), and   (e) the third conductor coupled to a second input (SPKL−) of the first speaker ( 238 L), a second input (SPKR−) of the second speaker ( 238 R), and a second output (MIC−) of the audio input module (MIC).       

     In another optional embodiment, the first speaker is a left stereo headset cup and the second speaker is an associated right stereo headset cup. 
     In another optional embodiment, the audio plug is selected from the group consisting of: a military pilot headset plug, and an Amphenol U-92 A/U plug. 
     In another optional embodiment, further including an audio jack ( 206 ) coupling the audio plug to an audio management module, the audio jack selected from the group consisting of: a military pilot headset plug, and an Amphenol U-93 A/U jack. 
     In another optional embodiment, wherein the first conductor is a speaker positive connection, the second conductor is a speaker negative connection, the third conductor is an audio input module negative connection, and the fourth conductor is an audio input module positive connection. 
     In another optional embodiment, including:
         an audio jack ( 206 ) having fifth ( 202 P), sixth ( 202 N), seventh ( 200 N), and eighth ( 200 P) conductors,   the fifth conductor coupled to the first conductor and configured for a first audio signal,   the sixth conductor coupled to the second conductor and configured for a second audio signal,   the eighth conductor coupled to the fourth conductor and configured for a fourth audio signal, and   the seventh conductor coupled to the third conductor and configured for a third audio signal.       

     In another optional embodiment, wherein:
         the first audio signal is a left stereo positive signal,   the second audio signal is a right stereo positive signal associated with the left stereo positive signal,   the fourth audio signal is a microphone positive signal, and   the third audio signal is a common ground.       

     In another optional embodiment, wherein the third conductor ( 100 N) is coupled by electrically shorting the second input (SPKL−) of the first speaker ( 238 L), the second input (SPKR−) of the second speaker ( 238 R), and the second output (MIC−) of the audio input module (MIC) at a location selected from the group consisting of: internal to the audio plug ( 104 ), and adjacent to the audio plug. 
     In another optional embodiment, wherein the audio input module includes a low impedance microphone ( 248 ) and a low-to-high impedance amplifier, the low impedance microphone coupled to a low impedance input of the low-to-high impedance amplifier, the first and second outputs of the audio module being high impedance outputs of the low-to-high impedance amplifier. 
     In another optional embodiment, wherein the a low-to-high impedance amplifier has an amplification selected from the group consisting of: on the order of 40 dB, on the order of 50 dB, and on the order of 60 dB. 
     In another optional embodiment, wherein the first and second speakers are high impedance speakers, the high impedance selected from the group consisting of: substantially 300 Ohms, on the order of 300 Ohms, substantially 600, and on the order of 600 Ohms. 
     In another optional embodiment, wherein the first and second speakers include noise reduction modules 
     In another optional embodiment, wherein the noise reduction modules are active noise reduction (ANR) modules and the first conductor and the third conductor provide phantom power to the active noise reduction modules. 
     In another optional embodiment, wherein the third conductor and the fourth conductor provide phantom power to the audio input module (MIC). 
     According to the teachings of the present embodiment there is provided a system ( 290 ) for conducting multiple analog signals (SPKL+, SPKR+, SPKL−, SPKN, MIC−, MIC+), the system including: an audio jack ( 206 ) having at least one conductor ( 200 N) receiving two or more signal leads ( 212 L−,  212 N,  210 N) at a common location ( 200 N), the two or more signal leads being shorted at a given distance from the common location 
     In an optional embodiment, further including an audio management module (AMS,  210 ): 
     (a) providing a first audio signal (SPKL+,  212 L) coupled via the audio jack ( 206 ) to a first input (SPKL+) of a first speaker ( 238 L), 
     (b) providing a second audio signal (SPKR+,  212 R) coupled via the audio jack ( 206 ) to a first input (SPKR+) of a second speaker ( 238 R), 
     (c) receiving a fourth audio signal (MIC+,  210 P) coupled via the audio jack ( 206 ) from a first output (MIC+) of an audio input module (AMP  246 ), and 
     (d) receiving a third audio signal ( 210 N, MIC−) coupled via the audio jack ( 206 ) from a second output (MIC−) of the audio input module (AMP  246 ), 
     (e) providing a speaker negative line ( 212 N) coupled via the audio jack ( 206 ) to both a second input (SPKL−) of the first speaker ( 238 L) and a second input (SPKR−) of the second speaker ( 238 R), 
     the third audio signal coupled to the speaker negative line. 
     In another optional embodiment, wherein the first audio signal is a speaker-left positive line, the second audio signal is a speaker-right positive line, the fourth audio signal is a microphone positive line, and the third audio signal is a microphone negative line. 
     In another optional embodiment, wherein the audio management module further provides a speaker-left negative line ( 212 L−, SPKL−) coupled to the second input of the first speaker, and the speaker negative line couples only to the second input of the second speaker, the microphone negative line, the speaker-left negative line, and the speaker negative line are commonly coupled. 
     In another optional embodiment, wherein the audio management module provides phantom power via one or more pairs of lines selected from the group consisting of: 
     (a) the speaker-left positive line and the speaker negative line, 
     (b) the speaker-right positive line and the speaker negative line, and 
     (c) the microphone positive line and the microphone negative line. 
     In another optional embodiment, wherein the third audio signal is coupled to the speaker negative line by electrically shorting the third audio signal and the speaker negative line at a location selected from the group consisting of: internal to an audio jack ( 206 ), and adjacent to the audio jack. In another optional embodiment, wherein the audio management module (AMS  210 ) provides phantom power to the first and second speakers ( 238 L,  238 R) via the first and third audio signals. In another optional embodiment, wherein the audio management module (AMS  210 ) provides phantom power to the audio input module (MIC) via the third and fourth audio signals. 
     While the current embodiment has been described with reference to a standard military pilot headset, this description is not limiting. Based on the current description, one skilled in the art will be able to implement the current invention for other configurations and deployments, including, but not limited to other military use, transportation, home, and consumer use. 
     The above description uses a preferred embodiment of using the stereo audio system  290  for 3D audio, however, this embodiment is not limiting. Embodiments of the system  290  can be used for non-3D audio, that is, a conventional stereo signal. The choices used to assist in the description of this embodiment should not detract from the validity and utility of the invention. It is foreseen that more general and alternative choices can be made, depending on the application. 
     The use of simplified calculations to assist in the description of this embodiment should not detract from the utility and basic advantages of the invention. 
     Note that a variety of implementations for modules and processing may be possible, depending on the application. The above description of modules is not limiting, and modules may be implemented at one or more locations. The above-described module functions may be combined and implemented as fewer modules or separated into sub-functions and implemented as a larger number of modules. Based on the above description, one skilled in the art will be able to design an implementation for a specific application. 
     Note that the above-described examples, numbers used, and exemplary calculations are to assist in the description of this embodiment. Inadvertent typographical errors, mathematical errors, and/or the use of simplified calculations do not detract from the utility and basic advantages of the invention. 
     To the extent that the appended claims have been drafted without multiple dependencies, this has been done only to accommodate formal requirements in jurisdictions that do not allow such multiple dependencies. Note that all possible combinations of features that would be implied by rendering the claims multiply dependent are explicitly envisaged and should be considered part of the invention. 
     It will be appreciated that the above descriptions are intended only to serve as examples, and that many other embodiments are possible within the scope of the present invention as defined in the appended claims.