WO2007072280A1 - Dispositif et procede destines au traitement de donnees audio - Google Patents

Dispositif et procede destines au traitement de donnees audio Download PDF

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Publication number
WO2007072280A1
WO2007072280A1 PCT/IB2006/054701 IB2006054701W WO2007072280A1 WO 2007072280 A1 WO2007072280 A1 WO 2007072280A1 IB 2006054701 W IB2006054701 W IB 2006054701W WO 2007072280 A1 WO2007072280 A1 WO 2007072280A1
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WO
WIPO (PCT)
Prior art keywords
amplitude
audio data
correction unit
audio
frequency range
Prior art date
Application number
PCT/IB2006/054701
Other languages
English (en)
Inventor
Julien L. Bergere
Original Assignee
Koninklijke Philips Electronics N.V.
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 Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2007072280A1 publication Critical patent/WO2007072280A1/fr

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G9/00—Combinations of two or more types of control, e.g. gain control and tone control
    • H03G9/02—Combinations of two or more types of control, e.g. gain control and tone control in untuned amplifiers
    • H03G9/12—Combinations of two or more types of control, e.g. gain control and tone control in untuned amplifiers having semiconductor devices
    • H03G9/14—Combinations of two or more types of control, e.g. gain control and tone control in untuned amplifiers having semiconductor devices for gain control and tone control
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G9/00—Combinations of two or more types of control, e.g. gain control and tone control
    • H03G9/005—Combinations of two or more types of control, e.g. gain control and tone control of digital or coded signals
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G9/00—Combinations of two or more types of control, e.g. gain control and tone control
    • H03G9/02—Combinations of two or more types of control, e.g. gain control and tone control in untuned amplifiers
    • H03G9/12—Combinations of two or more types of control, e.g. gain control and tone control in untuned amplifiers having semiconductor devices
    • H03G9/18—Combinations of two or more types of control, e.g. gain control and tone control in untuned amplifiers having semiconductor devices for tone control and volume expansion or compression

Definitions

  • the invention relates to a device for processing audio data.
  • the invention further relates to a method of processing audio data.
  • the invention relates to a program element.
  • the invention relates to a computer-readable medium.
  • WO 2005/004114 discloses a sound reproduction system comprising a digital audio signal input, a digital audio signal processor, and a digital audio signal output, wherein the digital signal processor comprises a high pass filter, a compression amplifier for compression and amplification of a signal within a signal amplitude range, and a clipper for clipping the signal above a clipping level.
  • the digital signal processor comprises a high pass filter, a compression amplifier for compression and amplification of a signal within a signal amplitude range, and a clipper for clipping the signal above a clipping level.
  • the parameters of the various elements such as cut-off frequency, order of the pass filter, gain, etc. are dependent on a measured noise level.
  • a device for processing audio data a method of processing audio data, a program element and a computer-readable medium according to the independent claims are provided.
  • a device for processing audio data comprising an amplitude detection unit adapted to detect an amplitude of the audio data, and a correction unit for selectively attenuating the amplitude of the audio data in a mid-to-high audible frequency range in case of detecting that the detected amplitude exceeds a predetermined threshold value.
  • a method of processing audio data is provided, the method comprising detecting an amplitude of the audio data, and selectively attenuating the amplitude of the audio data in a mid-to-high audible frequency range in case of detecting that the detected amplitude exceeds a predetermined threshold value.
  • a program element which, when being executed by a processor, is adapted to control or carry out a method of processing audio data having the above mentioned features.
  • a computer- readable medium in which a computer program is stored which, when being executed by a processor, is adapted to control or carry out a method of processing audio data having the above mentioned features.
  • the audio processing according to embodiments of the invention can be realized by a computer program, that is by software, or by using one or more special electronic optimization circuits, that is in hardware, or in hybrid form, that is by means of software components and hardware components.
  • the attenuation may be restricted to one or more special frequency intervals.
  • the mid-to-high audible frequency range is believed to be particularly prone to the generation of audio output, which frequency range a human listener in many cases perceives to be non-harmonic or to cause pain.
  • mid-to-high audible frequency range may particularly cover a frequency range above the bass regime, but below the treble regime.
  • the term mid-to-high audible frequency range may cover frequencies in the domain between 1 kHz and 20 kHz. Dividing the audible frequency spectrum in bass frequency, mid frequency and treble frequency sub-portions, the bass regime may remain undamped, the mid frequency regime may be damped, and of the treble regime, only a low- frequency portion may be damped, wherein a high-frequency portion of the treble regime may remain undamped.
  • the term "mid-to-high" audible frequency range may particularly be understood as a synonym for the term "high-midrange” frequencies, that is to say an audible frequency range between medium frequencies and high treble frequencies.
  • a harshness reduction for a sound system may be provided.
  • an attenuation of frequencies for instance, in the 1 kHz to 20 kHz range (preferably in the 2 kHz to 8 kHz range) may be implemented at any desired position in an audio reproduction system.
  • Embodiments of the invention may be active or passive implementations of the selective attenuation feature.
  • THD total harmonic distortion
  • a sound reproduction system for reproducing sound signals comprising correction elements designed to correct the loudness of the sound signal by reducing the output level of the sound signals in the mid-high frequency area.
  • the reduction of output at mid- high frequencies can be incremental and may be increased as the loudness reproduced by the system is increased. It may also be dynamic, changing with the music energy and/or spectral component.
  • Exemplary embodiments of the invention may have the advantage that a sound system may be prevented from sounding harsh when played loud. Furthermore, the system may prevent hearing damage thanks to a subjectively well-balanced frequency spectrum at all listening levels. Furthermore, corrections for harsh sounding systems may be performed even at moderate levels (earphones), and it may be possible to correct even more audible artefacts at high loudness.
  • Exemplary applications of embodiments of the invention are all fields in which an improvement of the sound experience by reducing discomfort or danger caused at high listening volume (healthcare aspect), is desired, and apply to all music or speech reproducing systems.
  • a portable audio device used with headphones like an MP3 player or a mobile phone
  • headphones and earphones sound and music reproduction systems equipped with loudspeakers, loudspeakers, night club sound systems, and music stage sound systems are exemplary fields of application of embodiments of the invention.
  • an audio device or sound system may be provided with harshness reduction for improving the perceived quality of the sound by sound level dependent attenuation of frequencies in the mid range frequency band.
  • audio Io gists lack precise or converging information allowing making a direct link between the frequency of a loud and annoying auditory signal, and hearing impairment resulting of exposures to this auditory signal. What is sure is that exposure to loud sounds can impair hearing, wherein different human listeners may have a different vulnerability to it.
  • earphones which sound well-balanced when played at reasonable loudness (good relative loudness of all parts of the reproduced spectrum) may sound quite harsh when played very loud (situation which naturally occurs when playing back sound in a noisy environment like in a car, for instance).
  • An acoustic engineer is faced with designing earphones that sound best at low or at high loudness. In practice, users need both, and especially should not be subject to too harsh sound at high listening levels (tiring or even painful in some cases).
  • the attenuation of mid-high frequencies can be down in an analog manner or in a digital manner.
  • the attenuation may be, for the sake of simplicity, performed in a preamplifier for systems having an amplifier and a pre-amplif ⁇ er, but can also be performed in the main amplifier, or at a system level in an architecture involving, for instance, a feedback loop including the loudspeaker, the amplifier, the pre-amplif ⁇ er, and any sound features (like an equalizer, a bass boost, a virtualizer).
  • a system built around the loudspeaker itself is also covered by embodiments of the invention.
  • the reduction of the audio amplitude in a frequency-dependent manner may be more pronounced in the area of the audible spectrum where the ear is the most sensitive and where the pain threshold is the lowest, which is the 3 kHz to 5 kHz region.
  • It can be applied as a static correction (for example in a manner of an "on/off feature activating a fixed equalization curve, which makes the sound less harsh if the system is playing loud and the feature is turned “on"), or as a dynamic one (mid-high frequency attenuation appears and increases as volume control is put to a louder position or as the complete amplified signal goes beyond a certain threshold, or as a part of the signal's spectrum reaches a certain relative value compared to the rest of the spectrum.
  • the dynamic implementations can be "on/off or blind (that is always "on", but has only effect when needed) features.
  • Exemplary fields of application of the invention are headphones and earphones with loudness protection, an algorithm for earphones for mobile applications, DSP chips for audio applications like symphony, headphones and speakers amplifiers, personal infotainment and mobile phones, earphones with integrated electronics, main mobile phones, portable audio devices and headphones.
  • the measures taken according to exemplary embodiments of the invention may yield the result that sound, even when played back at high volume, does not sound aggressive. Harshness may be compensated when the intensity level of the audio content is decreased in the mid- frequency range, depending on the loudness within an audio track.
  • the amplitude detection unit may be adapted to detect the amplitude of the audio data in a frequency-selective manner.
  • a frequency selective detection may be implemented to refine the basis for the decision to which extent in which frequency range an attenuation should be performed.
  • the amplitude detection unit may be adapted to detect the amplitude of the audio data in a "static" manner.
  • the attenuation parameters range of attenuated frequencies, extent or amount of attenuation, etc.
  • This may have the advantage that the attenuation may be adjusted constantly, for instance based on medical knowledge, so as to provide a medical security feature in an audio playback product that is in accordance with anatomic properties of an "average" human user.
  • a human listener may be securely prevented from hearing impairment when using such an audio playback product.
  • the amplitude detection unit may be adapted to detect the amplitude of the audio data in a "dynamic" manner, particularly based on current parameters of the audio content to be reproduced.
  • a dynamic configuration may provide a high degree of flexibility, since the parameters of attenuation as mentioned beforehand may be adjusted in a time-dependent manner and/or in an audio content-dependent manner in dependence of various parameters, for instance changing with music energy and/or spectral content.
  • the correction unit may be adapted for selectively attenuating the amplitude of the audio data in a frequency-dependent manner within the mid-to-high audible frequency range.
  • the attenuation in the mid-to-high audible frequency range does not necessarily has to be constant, but may take into account modifications within this range, for instance the fact that the human ear is very sensitive in the 3 kHz to 5 kHz range so that this sub-range of the mid-to-high audible frequency range may be attenuated in a stronger manner as compared to other frequency ranges within the mid-to-high audible frequency range.
  • the correction unit may be adapted for incrementally (particularly stepwise) attenuating the amplitude of the audio data. This may allow for a refined correction which may make sure that a human listener perceives the processed audio data stream to be of proper quality and to be non-disturbing.
  • the correction unit may be adapted for selectively attenuating the amplitude of the audio data within a frequency range between essentially 1 kHz and essentially 20 kHz, particularly between essentially 2 kHz and essentially 8 kHz. These frequency ranges are those in which the human ear is usually prone to a pain reception as a result of audio playback of a very high intensity.
  • the correction unit may further be adapted for selectively attenuating the amplitude of the audio data within a frequency range between essentially 3 kHz and essentially 5 kHz. This is a range that is considered to be the audio regime in which the sensitivity of the human ear is a maximum so that this range is particularly prone to a subjective pain perception.
  • the correction unit may further be adapted for selectively attenuating the amplitude of the audio data so that the attenuated amplitude does no longer exceed a predetermined loudness level.
  • a loudness level may be selected to be in accordance with legal frame conditions, or with frame conditions derived from experiments performed with human listeners indicating that exceeding a particular loudness level may cause pain for a significant percentage of human listeners.
  • the device may comprise a pre-amplifier and a main amplifier, wherein the amplitude detection unit and/or the correction unit may be located within the preamplifier positioned in an audio processing path preceding the main amplifier. Positioning the detection unit and the correction unit at such a position may be a very simple solution.
  • the amplitude detection unit and/or the correction unit may be located within the main amplifier positioned in an audio processing path succeeding the pre-amplifier.
  • the device may comprise an audio reproduction unit, and the amplitude detection unit and/or the correction unit may be located within the audio reproduction unit.
  • the device may be realized as an earphone, a loudspeaker, a night club sound system, a music stage sound system, a GSM device, headphones, a gaming device, a laptop, a portable audio player, a DVD player, a CD player, a harddisk-based media player, an internet radio device, a public entertainment device, an MP3 player, a hi-fi system, a vehicle entertainment device, a car entertainment device, a portable video player, a mobile phone, a medical communication system, a body-worn device, and a hearing aid device.
  • an embodiment of the invention may be implemented in audiovisual applications like a video player in which a loudspeaker is used, or a home cinema system.
  • Fig. 1 shows an audio data processing system according to an exemplary embodiment of the invention.
  • Fig. 2 shows an audio data processing system according to another exemplary embodiment of the invention.
  • the audio processing device 100 comprises an amplitude detection unit 101 adapted to detect an amplitude of audio data emitted by a source of digital audio signals 105 after having passed a sound feature unit 106 including components like an equalizer, a surround function, a dynamic bass boost, etc.
  • the processed audio stream is passed through a user controlled volume control unit 107.
  • a user of the system 100 may adjust a desired loudness by adjusting the volume control unit 107.
  • the processed stream 120 is guided through a harshness reduction unit 108 which may be switched “on” or “off according to the embodiment of Fig. 1.
  • Fig. 1 further shows a more detailed view of the internal constitution of the harshness reduction unit 108.
  • the audio data 120 provided at an input of the harshness reduction unit 108 leaves the harshness reduction unit 108 as audio data 121 that is supplied to a digital-to-analog converter (DAC) 109. From there, the data is supplied to an amplifier 103 with fixed gain, and may be passed to earphones 104 for reproduction, that is for emission of acoustic waves.
  • DAC digital-to-analog converter
  • the audio data 120 When the audio data 120 enters the harshness reduction unit 108, the audio data 120 is supplied to an input of the amplitude detection unit 101 that is adapted to detect an amplitude of the audio data 120.
  • detection may include a loudness-detection (for instance using a dBA filter), with the integration time constant.
  • the harshness reduction unit 108 comprises a correction unit 102 for selectively attenuating the amplitude of the audio data 120 in a mid-to-high audible frequency range in case of detecting, by the amplitude detection unit 101, that the amplitude exceeds the predetermined threshold value.
  • the correction unit 102 is realized as a notch filter having a frequency of 4 kHz, a Q-value of two (2) and a gain that is a function of an input signal L dB A provided by the amplitude detection unit 101.
  • an on/off switch unit 112 controls a first switch
  • the first switch 110 is closed and the second switch 111 is open so that the audio data 120 is passed through the correction unit 102, wherein the functionality of the correction unit 102 is controlled by the output signal of the amplitude detection unit 101.
  • the on/off control unit 112 (which may be user-controlled) may bring the first switch 110 in an open state and may simultaneously bring the second switch 111 in a closed state. Then, the correction unit 102 is bypassed by the audio data 120 so that, after having passed the adding unit 113, the audio data 120 is essentially identical to the audio data 121, that is to say no attenuation function is realized.
  • the amplitude detection unit 102 may detect the amplitude of the audio data
  • the correction unit 102 selectively attenuates the amplitude of the audio data 120 so that attenuated amplitude falls below a predetermined loudness level as defined by the loudness detection unit 101.
  • the function f giving the gain of the shelf filter 102 may be defined by playing a "100 dB test" test signal as the source signal, all other sound features being in the conditions that maximize the measured dBA level.
  • a suitable gain for the notch filter 102 is defined by listening (sound should be less harsh, but not too dull), for instance -12 dB.
  • L dBA L dBA max
  • f(L_dBA_max) -12 dB. Listening to different music tracks and deciding when the system's sound starts to be harsh may define a value L dBA min. Below L dBA min, the notch filter 102 has unity gain (0 dB).
  • the audio data processing unit 200 comprises a first section 210 representing a player (volume control at maximum), and comprises a second portion 220 representing headphones (with a volume control).
  • the player 210 has an amplifier 201 and an adjustable resistor 202 having resistor values between 0 and 20 Ohms.
  • the amplifier 201 has a ground connection 209.
  • An input of the headphone portion 220 is coupled to an output of the player portion 210 and comprises a resistor 203 (potentiometer) with an adjustable value of the resistance, between a minimum and a maximum value.
  • a resistor 203 potentiometer
  • the data traverses a notch filter 204 at 3.5 kHz and a Q-factor of (essentially) 3.
  • the notch filter 204 comprises a circuit of a capacitance 206, a resistor 207 and an inductance 208 which are connected parallel to one another.
  • the notch filter 204 has the function of a correction unit for selectively attenuating the amplitude of the audio data in a mid-to-high audible frequency range in case of detecting that the amplitude exceeds a predetermined threshold value.
  • the embodiment of Fig. 2 relates to headphones with volume control. It may be assumed that the output amplifier 201 of the player portion 210 has (essentially) 0 Ohm output impedance.
  • the headphone loudspeaker 205 is supplied with a signal having nearly the spectrum produced by the player 210.
  • the value of 500 Ohms slide resistor 203 and 48 Ohms resistor 207 can be tuned so as to provide virtually any desired notch correction, at "min” volume and at “max” volume. With the system 200, it is therefore also possible to correct for headphones that sound harsh even at moderate loudness (because they suffer, for instance, of a peak at 4 kHz in their frequency response).

Landscapes

  • Tone Control, Compression And Expansion, Limiting Amplitude (AREA)
  • Circuit For Audible Band Transducer (AREA)

Abstract

L'invention concerne un dispositif (100) destiné au traitement de données audio, ce dispositif (100) comprenant une unité de détection d'amplitude (101) conçue de manière à détecter l'amplitude des données audio, et une unité de correction (102) destinée à atténuer de manière sélective l'amplitude des données audio dans une gamme de fréquences sonores moyenne à élevée si l'amplitude détectée dépasse une valeur seuil prédéfinie.
PCT/IB2006/054701 2005-12-22 2006-12-08 Dispositif et procede destines au traitement de donnees audio WO2007072280A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP05112813 2005-12-22
EP05112813.0 2005-12-22

Publications (1)

Publication Number Publication Date
WO2007072280A1 true WO2007072280A1 (fr) 2007-06-28

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WO (1) WO2007072280A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102011078552A1 (de) * 2011-07-01 2013-01-03 Richard Witte Verfahren und Vorrichtungen zum Erzeugen eines Audiosignals

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999053615A2 (fr) * 1998-04-08 1999-10-21 Gingsjoe Anders Dispositif et procede destines a reduire les clics
EP1542359A1 (fr) * 2003-12-09 2005-06-15 Nec Corporation Appareil pour compression/expansion des signaux et dispositif mobile de communication
EP1601171A1 (fr) * 2004-05-28 2005-11-30 Research In Motion Limited Système, procédé pour régler un signal audio

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999053615A2 (fr) * 1998-04-08 1999-10-21 Gingsjoe Anders Dispositif et procede destines a reduire les clics
EP1542359A1 (fr) * 2003-12-09 2005-06-15 Nec Corporation Appareil pour compression/expansion des signaux et dispositif mobile de communication
EP1601171A1 (fr) * 2004-05-28 2005-11-30 Research In Motion Limited Système, procédé pour régler un signal audio

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102011078552A1 (de) * 2011-07-01 2013-01-03 Richard Witte Verfahren und Vorrichtungen zum Erzeugen eines Audiosignals
DE102011078552B4 (de) * 2011-07-01 2014-05-15 Solid Sound Labs UG (haftungsbeschränkt) Verfahren und Vorrichtungen zum Erzeugen eines Audiosignals

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