WO2008081403A1 - A method for reducing noise - Google Patents

A method for reducing noise Download PDF

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Publication number
WO2008081403A1
WO2008081403A1 PCT/IB2007/055337 IB2007055337W WO2008081403A1 WO 2008081403 A1 WO2008081403 A1 WO 2008081403A1 IB 2007055337 W IB2007055337 W IB 2007055337W WO 2008081403 A1 WO2008081403 A1 WO 2008081403A1
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WO
WIPO (PCT)
Prior art keywords
television
reducing noise
noise according
speaker
characteristic
Prior art date
Application number
PCT/IB2007/055337
Other languages
French (fr)
Inventor
Halit Kaan Ecder
Original Assignee
Grundig Elektronik Anonim Sirketi
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Grundig Elektronik Anonim Sirketi filed Critical Grundig Elektronik Anonim Sirketi
Publication of WO2008081403A1 publication Critical patent/WO2008081403A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/44—Receiver circuitry for the reception of television signals according to analogue transmission standards
    • H04N5/60—Receiver circuitry for the reception of television signals according to analogue transmission standards for the sound signals
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers without distortion of the input signal
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/32—Automatic control in amplifiers having semiconductor devices the control being dependent upon ambient noise level or sound level
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G5/00—Tone control or bandwidth control in amplifiers
    • H03G5/16—Automatic control
    • H03G5/165—Equalizers; Volume or gain control in limited frequency bands
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/41—Structure of client; Structure of client peripherals
    • H04N21/422—Input-only peripherals, i.e. input devices connected to specially adapted client devices, e.g. global positioning system [GPS]
    • H04N21/42204—User interfaces specially adapted for controlling a client device through a remote control device; Remote control devices therefor
    • H04N21/42206—User interfaces specially adapted for controlling a client device through a remote control device; Remote control devices therefor characterized by hardware details
    • H04N21/42222—Additional components integrated in the remote control device, e.g. timer, speaker, sensors for detecting position, direction or movement of the remote control, microphone or battery charging device
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/439—Processing of audio elementary streams
    • H04N21/4394—Processing of audio elementary streams involving operations for analysing the audio stream, e.g. detecting features or characteristics in audio streams
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/442—Monitoring of processes or resources, e.g. detecting the failure of a recording device, monitoring the downstream bandwidth, the number of times a movie has been viewed, the storage space available from the internal hard disk
    • H04N21/44231—Monitoring of peripheral device or external card, e.g. to detect processing problems in a handheld device or the failure of an external recording device
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/47—End-user applications
    • H04N21/485—End-user interface for client configuration
    • H04N21/4852—End-user interface for client configuration for modifying audio parameters, e.g. switching between mono and stereo

Definitions

  • the present invention relates to a noise reduction method developed for reducing the noise generated due to various reasons in televisions and similar electronic devices.
  • Deep noise test value is defined as the noise measured electrically or acoustically, when the device is not receiving any audio signal from any audio source and is at the maximum sound level.
  • the filtering methods in the state of the art also filter many sounds in the frequencies which normally cannot be heard by the user and thus do not have to be filtered.
  • the reasons of this can be that the filtering is applied to sounds which cannot be output by the speakers or to sounds which cannot be heard because of the sound level in the external environment in which the television is used.
  • the objective of the present invention is to realize a method for reducing noise, used in televisions, which dynamically filters the noise frequencies which can only be heard by the user according to the instantaneous changes in the conditions.
  • Figure 1 is the block diagram of an example embodiment of the inventive method for reducing noise.
  • Figure 2 is the table including the data recorded in an example embodiment of the inventive method for reducing noise.
  • the inventive method for reducing noise basically determines the characteristic of the speaker on the television and detects noises originating from the television or external sources; and afterwards, according to these two data, reveals a filter characteristic that will filter the noise at the frequencies which can only be output by the speaker. Subsequently, it detects the sound level at the external environment where the television is used, and according to this sound level, it activates or deactivates the filter whose characteristic is determined.
  • the inventive method Before the inventive method is started to be applied, preferably the user is firstly prompted whether he/she desires to activate the inventive method for reducing noise. After that, when the inventive method is activated, it is checked if any external device (DVD player, etc.) is connected to the television.
  • any external device DVD player, etc.
  • the sound processor When the characteristic of the speaker is being determined, the sound processor generates a sweep audio signal by means of the generator contained therein. As a result of this signal, as required by the environmental conditions and design of the speaker, due to the acoustic impedance change, frequency dependend different voltage values are measured on the reference resistor.
  • the frequency depended impedance information obtained by the said measurement are kept in a memory. These data play a significant role in determination of the characteristic of the filter to be used in the subsequent stages of the method. Since the purpose here is to filter the undesired noises before they transform into physical sound waves, information related to which frequency will transform into a physical sound wave of which intensity is important from the point of the characteristic of the filter to be used.
  • Another advantage brought by this stage of the method is ensuring that the system foresees the differences that will arise in the case of changing the speaker or the television, and ability to change the characteristic of the filter in line with this change without requiring any additional interference.
  • noises originating from the television and the external devices (DVD player, etc.) connected to the televisions are measured. All sources supported by the device are swept one by one and fast Fourier transform analysis of the existing noise signal is performed. This way, frequency characteristic and amplitude information of the existing noise are obtained. This information is kept for later as the frequency and amplitude information to be used later in the other stages.
  • the characteristic of the filter to be applied is determined and saved.
  • information gathered related to the frequency depended impedance change of the speaker provides information regarding the performance of the acoustic structure (E.g. Fo frequency and high cut-off frequency).
  • the filter performs maximum reduction at the region below the Fo frequency.
  • the impedance information of 1 KHz approximately which regions the acoustic high cut-off frequency refers to is determined.
  • the sound level at the environment where the user is listening and the probability of the noise generated by the external device to be heard in this environment are determined via a microphone disposed on the remote control.
  • the sound level information received by the microphone disposed on the television remote control, at the moment when the television is turned on but has not yet output any sound, is considered as the sound level value of the environment.
  • the obtained sound level value of the environment is saved to be used at the last stage of the method.
  • the sound level of the environment by detecting the signal coming from the television, the sound level of the environment, where listening is realized, can be determined at the moment when the signal coming from the transmission is interrupted. This way, sound level information of the environment can be updated optionally in certain intervals during operation of the television.
  • the environment sound level measurement result is compared with the acoustic deep noise test value determined as a result of the acoustic tests conducted at the production plant of the television in which the related method is used previously, and saved in the device.
  • the filter whose characteristic is predetermined is either activated or left inactive. For example, if the value of the deep noise test conducted at the production plant is measured as 40db and the environment sound level as 50 db, the noise coming from the television is assumed that it cannot be heard and no filtering is performed. However, if the sound level in the environment is at a level which allows the noise to be audible, the filters are activated.
  • the reduction coefficients to be used by the filters are determined via the information obtained about the characteristics of the noises originating from television and external devices (DVD player, etc.) connected to the television. Activation or deactivation of the filter is determined as a result of the comparison made with the acoustic deep noise test value.
  • a sound processor (1) an amplifier (2), a microcontroller (3), an impedance sensor (4), a coefficient table (5), a speaker (6), a reference resistor (7) and an analyzer and filter (8).
  • the inventive method can be applied to all electronic devices which amplify electrical audio signal therein and generate physical sound waves via the speakers they are connected to.

Abstract

The present invention relates to a noise reduction method for reducing the noise generated due to various reasons in televisions and similar electronic devices. The objective of the present invention is to realize a method for reducing noise, used in televisions, which dynamically filters the noise frequencies which can only be heard by the user according to the instantaneous changes in the conditions. For that purpose, a method for reducing noise is realized and thus a solution has been provided to the problem, which method determines the speaker characteristic of the television, noises originating from televisions and external devices (DVD player, etc.) connected to televisions and the sound level in the external environment where the television is used; and according to these information dynamically filters the noises which can only be heard by the user.

Description

Description A METHOD FOR REDUCING NOISE
[ 1 ] Field of the Invention
[2] The present invention relates to a noise reduction method developed for reducing the noise generated due to various reasons in televisions and similar electronic devices.
[3] Background of the Invention
[4] There is a wide variety of reasons for the generation of noise in televisions and similar electronic devices. For example, layout designs of the circuit components of the concerned electronic devices (ground placement, noise coupling by various sources near audio carrying tracks, etc.), noises disseminated by the sound components used before the amplifier within themselves, noises originating from audio sources and the audio carrying tracks connected thereto are some of the reasons of the generation of noise in televisions.
[5] All of these noises have a negative impact on the parameters of S/N ratio, deep noise, etc. which are of the audio performance parameters of the device. As a result of this, users are subject to disturbing sound output.
[6] All of the noises which occur when the device is not receiving any audio signal from the audio source can be named as deep noise. Deep noise test value is defined as the noise measured electrically or acoustically, when the device is not receiving any audio signal from any audio source and is at the maximum sound level.
[7] In the state of the art, there are many methods realized to prevent this noise problem occurring in electronic devices. The Japanese patent application No. JPl 1331777 and the USA patent application No. US2002154761 are two examples of the said type of methods. Methods preventing the noise problem generally work with the principle of overcoming noise by filtering the frequencies including these noises.
[8] However, the filtering methods in the state of the art also filter many sounds in the frequencies which normally cannot be heard by the user and thus do not have to be filtered. The reasons of this can be that the filtering is applied to sounds which cannot be output by the speakers or to sounds which cannot be heard because of the sound level in the external environment in which the television is used.
[9] Furthermore, in the state of the art, an effective and adequate filtering cannot be performed, since the characteristic of the speaker on the television and the information depending on instantaneous situations like noises originating from televisions and external devices (DVD player, etc.) connected to televisions and sound level in the external environment where the television is used, cannot be determined. For example, factors like replacement of the speaker on the television or replacement of the television itself, use of the television with different external devices, increase or decrease in the environment sound level are not taken into consideration in these filtering systems.
[10] Summary of the Invention
[11] The objective of the present invention is to realize a method for reducing noise, used in televisions, which dynamically filters the noise frequencies which can only be heard by the user according to the instantaneous changes in the conditions.
[12] For that purpose, a method for reducing noise is realized and thus a solution has been provided to the problem, which method determines the speaker characteristic of the television, noises originating from televisions and external devices (DVD player, etc.) connected to televisions and the sound level in the external environment where the television is used; and according to these information dynamically filters the noises which can only be heard by the user.
[13] Detailed Description of the Invention
[14] The method for reducing noise realized to fulfill the objectives of the present invention is illustrated in the accompanying figures, in which;
[15] Figure 1 is the block diagram of an example embodiment of the inventive method for reducing noise.
[16] Figure 2 is the table including the data recorded in an example embodiment of the inventive method for reducing noise.
[17] The parts in the figures are numbered individually where the numbers refer to the following:
[18] 1. Sound processor
[19] 2. Amplifier
[20] 3. Microcontroller
[21] 4. Impedance sensor
[22] 5. Coefficient table
[23] 6. Speaker
[24] 7. Reference resistor
[25] 8. Analyzer and filter
[26] The inventive method for reducing noise basically determines the characteristic of the speaker on the television and detects noises originating from the television or external sources; and afterwards, according to these two data, reveals a filter characteristic that will filter the noise at the frequencies which can only be output by the speaker. Subsequently, it detects the sound level at the external environment where the television is used, and according to this sound level, it activates or deactivates the filter whose characteristic is determined.
[27] Before the inventive method is started to be applied, preferably the user is firstly prompted whether he/she desires to activate the inventive method for reducing noise. After that, when the inventive method is activated, it is checked if any external device (DVD player, etc.) is connected to the television.
[28] As speakers exhibit frequency depended impedance change depending on the mechanism they are mounted on and the volume in which they are employed, it is expected that they exhibit a frequency dependent impedance change also depending on the television onto which they are connected. As a result of this change, the speaker will not be able to exhibit the same acoustic efficiency for audio signals at different frequencies having equal amplitudes. For that reason, the characteristics of the speaker on the device on which it is operational at that moment and its audio output capabilities should be determined. For this purpose, acoustic impedance characteristic of the speaker on the television should be determined.
[29] When the characteristic of the speaker is being determined, the sound processor generates a sweep audio signal by means of the generator contained therein. As a result of this signal, as required by the environmental conditions and design of the speaker, due to the acoustic impedance change, frequency dependend different voltage values are measured on the reference resistor.
[30] The frequency depended impedance information obtained by the said measurement are kept in a memory. These data play a significant role in determination of the characteristic of the filter to be used in the subsequent stages of the method. Since the purpose here is to filter the undesired noises before they transform into physical sound waves, information related to which frequency will transform into a physical sound wave of which intensity is important from the point of the characteristic of the filter to be used.
[31] Another advantage brought by this stage of the method is ensuring that the system foresees the differences that will arise in the case of changing the speaker or the television, and ability to change the characteristic of the filter in line with this change without requiring any additional interference.
[32] After the characteristic of the television speaker is determined, noises originating from the television and the external devices (DVD player, etc.) connected to the televisions are measured. All sources supported by the device are swept one by one and fast Fourier transform analysis of the existing noise signal is performed. This way, frequency characteristic and amplitude information of the existing noise are obtained. This information is kept for later as the frequency and amplitude information to be used later in the other stages.
[33] After the characteristic of the speaker on the television and the characteristics of the noises originating from televisions and external devices (DVD player, etc.) connected to televisions are detected and saved, the characteristic of the filter to be applied is determined and saved. At this point, information gathered related to the frequency depended impedance change of the speaker provides information regarding the performance of the acoustic structure (E.g. Fo frequency and high cut-off frequency). The filter performs maximum reduction at the region below the Fo frequency. Preferably, in line with the impedance information of 1 KHz, approximately which regions the acoustic high cut-off frequency refers to is determined.
[34] After the characteristic of the filter to be applied is determined, the sound level at the environment where the user is listening and the probability of the noise generated by the external device to be heard in this environment are determined via a microphone disposed on the remote control. The sound level information received by the microphone disposed on the television remote control, at the moment when the television is turned on but has not yet output any sound, is considered as the sound level value of the environment. The obtained sound level value of the environment is saved to be used at the last stage of the method.
[35] Preferably, by detecting the signal coming from the television, the sound level of the environment, where listening is realized, can be determined at the moment when the signal coming from the transmission is interrupted. This way, sound level information of the environment can be updated optionally in certain intervals during operation of the television.
[36] The environment sound level measurement result is compared with the acoustic deep noise test value determined as a result of the acoustic tests conducted at the production plant of the television in which the related method is used previously, and saved in the device. According to the outcome of the comparison, the filter whose characteristic is predetermined is either activated or left inactive. For example, if the value of the deep noise test conducted at the production plant is measured as 40db and the environment sound level as 50 db, the noise coming from the television is assumed that it cannot be heard and no filtering is performed. However, if the sound level in the environment is at a level which allows the noise to be audible, the filters are activated. The reduction coefficients to be used by the filters are determined via the information obtained about the characteristics of the noises originating from television and external devices (DVD player, etc.) connected to the television. Activation or deactivation of the filter is determined as a result of the comparison made with the acoustic deep noise test value.
[37] In an example embodiment of the invention illustrated in Figure 1, there are provided a sound processor (1), an amplifier (2), a microcontroller (3), an impedance sensor (4), a coefficient table (5), a speaker (6), a reference resistor (7) and an analyzer and filter (8).
[38] On the television where the inventive method is realized, there can be a plurality of speakers as well as one speaker. Furthermore the speaker(s) can also be externally connected to the television. Additionally, as there can be one or more speakers on the television where the inventive method is realized, one or more speakers can also be connected to the television at the same time. [39] The inventive method can be applied to all electronic devices which amplify electrical audio signal therein and generate physical sound waves via the speakers they are connected to. [40] Within the framework of the basic principles described herein, development of various embodiments of the invention is possible, and the details of the invention which are not described herein are obvious to the person skilled in the art. The invention is essentially according to the claims.

Claims

Claims
[ 1 ] A method for reducing noise which determines the characteristic of the speaker on the television, detects noises originating from the television or external sources, detects the sound level at the external environment where the television is used, characterized in that, it reveals a filter characteristic that will filter the noises according to the speaker characteristic, and the characteristics of the noises originating from the television or the external sources, and that it activates or deactivates this filter whose characteristic is determined, according to the external environment sound level information.
[2] A method for reducing noise according to Claim 1, characterized in that before the inventive method is started to be applied, the user is prompted whether he/she desires to activate the inventive method for reducing noise.
[3] A method for reducing noise according to Claim 2, characterized in that when the inventive method is activated, it is checked if any external device (DVD player, etc.) is connected to the television.
[4] A method for reducing noise according to any of the preceding claims, characterized in that the characteristic of the speaker on the television is determined.
[5] A method for reducing noise according to any of the preceding claims, characterized in that, within the application which reveals the characteristic of the speaker of the television, the sound processor generates a sweep audio signal by means of the generator contained therein.
[6] A method for reducing noise according to Claim 5, characterized in that, as a result of the said signal, as required by the environmental conditions and design of the speaker, due to the acoustic impedance change, frequency depended different voltage values are measured on a reference resistor and these values are saved.
[7] A method for reducing noise according to any of the preceding claims, characterized in that after the characteristic of the television speaker is determined, the noises originating from the television and external devices (DVD player, etc.) connected to the televisions are measured.
[8] A method for reducing noise according to any of the preceding claims, characterized in that all of the sources supported by the device are swept one by one and fast Fourier transform analysis of the existing noise signal is performed.
[9] A method for reducing noise according to any of the preceding claims, characterized in that frequency characteristic and amplitude information of the existing noises are obtained and saved as the measurement results of the noises originating from the television and external devices (DVD player, etc.) connected to the televisions.
[10] A method for reducing noise according to any of the preceding claims, characterized in that after the characteristic of the speaker on the television and the characteristics of the noises originating from televisions and external devices (DVD player, etc.) connected to televisions are detected and saved, the characteristic of the filter to be applied is determined and saved.
[11] A method for reducing noise according to any of the preceding claims, characterized in that by using the information such as Fo frequency and high cut-off frequency gathered about the performance of the acoustic structure of the speaker, the filter characteristic is determined so as to realize the maximum reduction at the region below the Fo frequency.
[12] A method for reducing noise according to any of the preceding claims, characterized in that in line with the impedance information of 1 KHz, approximately which regions the acoustic high cut-off frequency corresponds to is determined.
[13] A method for reducing noise according to any of the preceding claims, characterized in that after the characteristic of the filter to be applied is determined, the sound level at the environment where the user is listening and the probability of the noise generated by the external device to be heard in this environment are determined via a microphone.
[14] A method for reducing noise according to Claim 13 wherein the said microphone is disposed in the television remote control.
[15] A method for reducing noise according to any of the preceding claims, characterized in that the sound level information received by the microphone, at the moment when the television is turned on but has not yet output any sound, is considered and saved as the environment sound level.
[16] A method for reducing noise according to any of the preceding claims, characterized in that upon detection of the signal coming to the television, the sound level of the environment, where listening is realized, is determined at the moment when the signal coming from the transmission is interrupted and it is considered and saved as the sound level of the environment.
[17] A method for reducing noise according to any of the preceding claims, characterized in that environment sound level value is updated optionally, by means of the method described in Claim 16, in certain intervals during operation of the television.
[18] A method for reducing noise according to any of the preceding claims, characterized in that the environment sound level measurement result is compared with the acoustic deep noise test value determined as a result of the acoustic tests conducted at the production plant of the television and saved in the device.
[19] A method for reducing noise according to any of the preceding claims, characterized in that according to the outcome of the comparison, the filter whose characteristic is predetermined is either activated or left inactive.
[20] A method for reducing noise according to any of the preceding claims, characterized in that the said speaker is positioned on the television.
[21] A method for reducing noise according to any of the claims 1 to 19, characterized in that the said speaker is externally connected to the television.
[22] A method for reducing noise according to any of the claims 1 to 19, characterized in that the said speaker is a speaker group comprising a plurality of speakers either positioned on the television or externally connected to the television.
[23] A method for reducing noise according to any of the preceding claims, characterized in that an electronic device, which amplifies electrical audio signal and generates physical sound waves via the speakers it is connected to, is used in place of the said television.
PCT/IB2007/055337 2006-12-29 2007-12-28 A method for reducing noise WO2008081403A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
TR200607686 2006-12-29
TR2006/07686 2006-12-29

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Publication Number Publication Date
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3157169A4 (en) * 2014-06-10 2018-02-28 D&M Holdings, Inc. Audio system, audio device, mobile terminal device and audio signal control method

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US5627746A (en) * 1992-07-14 1997-05-06 Noise Cancellation Technologies, Inc. Low cost controller
US5974155A (en) * 1997-04-15 1999-10-26 The University Of Dayton System and method for actively damping boom noise
US6370254B1 (en) * 1990-09-11 2002-04-09 Concourse Communications Limited Audio-visual reproduction
US6584201B1 (en) * 1998-07-07 2003-06-24 Lucent Technologies Inc. Remote automatic volume control apparatus
US20050063552A1 (en) * 2003-09-24 2005-03-24 Shuttleworth Timothy J. Ambient noise sound level compensation
US20050207583A1 (en) * 2004-03-19 2005-09-22 Markus Christoph Audio enhancement system and method
US20060025994A1 (en) * 2004-07-20 2006-02-02 Markus Christoph Audio enhancement system and method
US20060251261A1 (en) * 2005-05-04 2006-11-09 Markus Christoph Audio enhancement system

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Publication number Priority date Publication date Assignee Title
US6370254B1 (en) * 1990-09-11 2002-04-09 Concourse Communications Limited Audio-visual reproduction
US5627746A (en) * 1992-07-14 1997-05-06 Noise Cancellation Technologies, Inc. Low cost controller
US5450494A (en) * 1992-08-05 1995-09-12 Mitsubishi Denki Kabushiki Kaisha Automatic volume controlling apparatus
US5974155A (en) * 1997-04-15 1999-10-26 The University Of Dayton System and method for actively damping boom noise
US6584201B1 (en) * 1998-07-07 2003-06-24 Lucent Technologies Inc. Remote automatic volume control apparatus
US20050063552A1 (en) * 2003-09-24 2005-03-24 Shuttleworth Timothy J. Ambient noise sound level compensation
US20050207583A1 (en) * 2004-03-19 2005-09-22 Markus Christoph Audio enhancement system and method
US20060025994A1 (en) * 2004-07-20 2006-02-02 Markus Christoph Audio enhancement system and method
US20060251261A1 (en) * 2005-05-04 2006-11-09 Markus Christoph Audio enhancement system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3157169A4 (en) * 2014-06-10 2018-02-28 D&M Holdings, Inc. Audio system, audio device, mobile terminal device and audio signal control method

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