EP0975201A2 - Verfahren zur Mehrkanal-Tonsignalverarbeitung - Google Patents

Verfahren zur Mehrkanal-Tonsignalverarbeitung Download PDF

Info

Publication number
EP0975201A2
EP0975201A2 EP99305562A EP99305562A EP0975201A2 EP 0975201 A2 EP0975201 A2 EP 0975201A2 EP 99305562 A EP99305562 A EP 99305562A EP 99305562 A EP99305562 A EP 99305562A EP 0975201 A2 EP0975201 A2 EP 0975201A2
Authority
EP
European Patent Office
Prior art keywords
distance
optimal amount
transaural
angle
ear
Prior art date
Legal status (The legal status 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 status listed.)
Granted
Application number
EP99305562A
Other languages
English (en)
French (fr)
Other versions
EP0975201B1 (de
EP0975201A3 (de
Inventor
Alastair Sibbald
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Creative Technology Ltd
Original Assignee
Central Research Laboratories Ltd
Creative Technology Ltd
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 Central Research Laboratories Ltd, Creative Technology Ltd filed Critical Central Research Laboratories Ltd
Publication of EP0975201A2 publication Critical patent/EP0975201A2/de
Publication of EP0975201A3 publication Critical patent/EP0975201A3/de
Application granted granted Critical
Publication of EP0975201B1 publication Critical patent/EP0975201B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S1/00—Two-channel systems
    • H04S1/002—Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution

Definitions

  • This invention relates to a method of processing a plural channel audio signal including left and right channels, the information in the channels representing a three dimensional sound-field for generation by respective left and right loudspeakers arranged at a given distance from the preferred position of a listener in use.
  • the fundamental Head Response Transfer Function (HRTF) characteristics which are required to implement a transaural crosstalk cancellation scheme are the left- and right-ear transfer functions associated with the azimuth angle at which the loudspeakers are situated ( Figure 1). For most applications, this is commonly accepted to be ⁇ 30°.
  • the near-ear function is sometimes referred to as the "same” side function (or “ S " function), and the far-ear function as the “alternate” (or " A ”) function.
  • S the near-ear function
  • A the far-ear function
  • Transaural crosstalk cancellation is described in more detail in WO 95/15069.
  • HRTFs measured by the prior art methods do not contain LF information, although, of course, the LF response is present in reality.
  • the results of a typical HRTF measurement are shown in Figure 3, depicting the A and S functions at 30° azimuth, measured from a commercial artificial head.
  • the uncertainty in the non-valid data, below several hundred Hz, is apparent. Accordingly, the missing LF properties must be replaced in order to create valid HRTFs, and this is conveniently done by extrapolating the amplitude data at the lowest valid frequency (200 Hz) back to 0 Hz (or in practise, back to the lowest practical frequency, say 10 Hz).
  • transaural crosstalk is defined to be the intensity ratio of the far ear signal with respect to the near ear signal. As these two functions have a different frequency dependence, this ratio will in general be a function of frequency. However, in the prior art the ratio approaches unity at low frequencies because A and S are forced to the same value below about 200 Hz. That is, the transaural crosstalk signal (far ear signal) is equal in magnitude to the primary signal (near ear signal) for such low frequencies.
  • the transaural crosstalk signal is substantially equal to (100% of) the primary signal at low frequencies, regardless of loudspeaker distance and/or angle. Consequently, all the prior art methods of transaural crosstalk cancellation have not been optimal for the arrangements/distances of loudspeakers used in practice.
  • the invention provides a means for creating optimal transaural crosstalk cancellation particularly, though not exclusively, for users of Personal Computer (PC) - based multimedia systems, in which the loudspeakers are relatively dose to the listener and might be at a variety of differing angles and distances, depending on the individual user's set-up configuration and preferences.
  • the amount of transaural crosstalk which occurs is also influenced by the angle of the loudspeakers. (Note that this is not to be confused with the use of the appropriate azimuth angle A and S functions, which is well known: i.e. use 30° A and S functions for speakers at 30°;15° A and S functions for speakers at 15°, and so on).
  • the present invention is a transaural crosstalk cancellation means based on "standard", 1 metre A and S functions.
  • the method employs an algorithm which controls the intensity of the transaural crosstalk cancellation signal relative to the near-ear intensity, using a crosstalk cancellation factor which is a function of loudspeaker proximity and spatial position.
  • the invention is based on the observation that when a sound source moves relatively closely towards the head (say, from a distance of several metres), then the individual far- and near-ear properties of the HRTF do not change a great deal in terms of their spectral properties, but their amplitudes, and the amplitude difference between them, do change substantially, caused by a distance ratio effect.
  • loudspeaker position angles lie in the range ⁇ 10° (for notebook PCs) to ⁇ 30° (for desktop PCs), and the distances (loudspeaker to ear) range from about 0.2 metres to 1 metre respectively. These ranges will be used here for illustrative purposes, but of course the invention is not restricted to these parameters.
  • the distance ratio (far-ear to sound source vs. near-ear to sound source) becomes greater.
  • the intensity of a sound source diminishes with distance as the energy of the propagating wave is spread over an increasing area.
  • the wavefront is similar to an expanding bubble, and hence the energy density is related to the surface area of the propagating wavefront, which is related by a square law to the distance travelled (the radius of the bubble). This is described in the Appendix.
  • the intensity ratios of left and right channels are related to the ratio of the squares of the distances.
  • the intensity ratios for the above examples at distances of 1 m, 0.5 m and 0.2 m are approximately 0.80, 0.62 and 0.35 respectively. In dB units, these ratios are -0.97 dB, -2.08 dB and -4.56 dB respectively.
  • Figure 5 shows a diagram of the near space around the listener, together with the reference planes and axes which will be referred to during the following descriptions, in which P-P' represents the front-back axis in the horizontal plane, intercepting the centre of the listener's head, and with Q-Q' representing the corresponding lateral axis from left to right.
  • the near-ear distance can be determined, for example, by the following calculation.
  • Figure 6 shows a plan view of the listener's head, together with the near area surrounding it.
  • Figure 7 shows a plan view of the listener's head, together with the near area surrounding it.
  • the "true" source-to-ear paths for the close frontal positions such as path "A”
  • path "B" the direct distance
  • the angle subtended by S-head_centre-Q' is (90° - ⁇ ).
  • the near-ear distance can be derived using the cosine rule, from triangle S-head_centre-near_ear: If we assume the head radius, r, is 7.5 cm, then p is given by:
  • the far-ear distance can be determined, for example, by the following calculation.
  • Figure 8 shows a plan view of the listener's head, together with the near-field area surrounding it.
  • the path between the sound source and the far-ear comprises two serial elements, as is shown dearly in the right hand detail of Figure 8.
  • the distance from the sound source to the centre of the head is d, and the head radius is r.
  • the angle subtended by the tangent point and the head centre at the source is angle R.
  • the circumferential path can be calculated from this angle, and is: Hence, by substituting (7) into (8), and combining with (6), an expression for the total distance (in cm) from sound source to far-ear for a 7.5 cm radius head can be calculated:
  • the crosstalk factor which is the ratio of (far-ear/near-ear) intensities, as a fraction or percentage of this limiting, 100% value.
  • This would define how much attenuation should be applied to the crossfeed path in a transaural crosstalk cancellation system ("C" in Figure 2) based on conventional "infinitely distant" A and S functions.
  • the crosstalk cancellation factor, X could be converted into dB units of sound intensity, X(dB) and used to define the LF asymptote difference of an A and S function pair, as shown in Figure 9, which could then be used in a conventional crosstalk cancellation scheme (for example Figure 2, corresponding to Atal and Schroeder, US 3,236,949) to the same effect.
  • Figure 2 corresponding to Atal and Schroeder, US 3,236,949
  • the A function LF asymptote would be set so as to lie X(dB) below the S asymptote (because the far (A) ear is always more distant).
  • the crosstalk factor X is the far-ear LF intensity (I F ) expressed as a fraction of the near-ear LF intensity (I N ).
  • the intensities are related to the distances from the source to far-ear (D F ) and near-ear (D N ) by the square law relationship (see Appendix), as follows.
  • I F I N D 2 N D 2 F
  • the near-ear distance is:
  • the far-ear distance is:
  • the crosstalk factor X i.e. the LF intensity ratio
  • the transaural crosstalk cancellation factor X is incorporated into the filter design procedure, thus allowing a range of different transaural crosstalk cancellation filters to be created from standard low frequency convergent A and S functions, but with differing values of X, for a range of speaker configurations, such that the end user can select the most appropriate one for their particular speaker configuration.
  • a range of filters for X values in the range say, 0.5 to 1.0 in 0.05 increments.
  • a further disadvantage of this alternative approach is that it would require many measurements at different distances and angles, and would result in quantised-distance effects: an optimum value could not be calculated and easily be provided for all loudspeaker configurations.
  • the present invention allows both distance and angle parameters to be used to calculate a single crosstalk cancellation factor, from which an associated filter is selected, based on accurate, 1 metre measurement.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Stereophonic System (AREA)
  • Stereophonic Arrangements (AREA)
  • Circuit For Audible Band Transducer (AREA)
EP99305562.3A 1998-07-24 1999-07-12 Verfahren zur Mehrkanal-Tonsignalverarbeitung Expired - Lifetime EP0975201B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9816059A GB2340005B (en) 1998-07-24 1998-07-24 A method of processing a plural channel audio signal
GB9816059 1998-07-24

Publications (3)

Publication Number Publication Date
EP0975201A2 true EP0975201A2 (de) 2000-01-26
EP0975201A3 EP0975201A3 (de) 2005-06-08
EP0975201B1 EP0975201B1 (de) 2013-04-10

Family

ID=10836042

Family Applications (1)

Application Number Title Priority Date Filing Date
EP99305562.3A Expired - Lifetime EP0975201B1 (de) 1998-07-24 1999-07-12 Verfahren zur Mehrkanal-Tonsignalverarbeitung

Country Status (3)

Country Link
EP (1) EP0975201B1 (de)
JP (1) JP2000059892A (de)
GB (1) GB2340005B (de)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4835185B2 (ja) * 2006-02-08 2011-12-14 ソニー株式会社 オーディオ信号出力装置および音漏れ低減方法
US9094771B2 (en) 2011-04-18 2015-07-28 Dolby Laboratories Licensing Corporation Method and system for upmixing audio to generate 3D audio
KR101687493B1 (ko) * 2015-08-12 2016-12-16 연세대학교 산학협력단 Ftn 시스템에서 신호 전송 방법 및 장치
CN111587582B (zh) * 2017-10-18 2022-09-02 Dts公司 用于3d音频虚拟化的音频信号预调节的系统、方法、以及存储介质
WO2020107192A1 (zh) * 2018-11-27 2020-06-04 深圳市欢太科技有限公司 立体声播放方法、装置、存储介质及电子设备

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5832840B2 (ja) * 1977-09-10 1983-07-15 日本ビクター株式会社 立体音場拡大装置
JPH07105999B2 (ja) * 1990-10-11 1995-11-13 ヤマハ株式会社 音像定位装置
GB9324240D0 (en) * 1993-11-25 1994-01-12 Central Research Lab Ltd Method and apparatus for processing a bonaural pair of signals
JPH10108300A (ja) * 1996-09-27 1998-04-24 Yamaha Corp 音場再生装置
GB9622773D0 (en) * 1996-11-01 1997-01-08 Central Research Lab Ltd Stereo sound expander
GB2334867A (en) * 1998-02-25 1999-09-01 Steels Elizabeth Anne Spatial localisation of sound

Also Published As

Publication number Publication date
GB2340005A (en) 2000-02-09
EP0975201B1 (de) 2013-04-10
JP2000059892A (ja) 2000-02-25
GB2340005B (en) 2003-03-19
EP0975201A3 (de) 2005-06-08
GB9816059D0 (en) 1998-09-23

Similar Documents

Publication Publication Date Title
US6643375B1 (en) Method of processing a plural channel audio signal
Schärer et al. Evaluation of equalization methods for binaural signals
US9635484B2 (en) Methods and devices for reproducing surround audio signals
US4739513A (en) Method and apparatus for measuring and correcting acoustic characteristic in sound field
US10706869B2 (en) Active monitoring headphone and a binaural method for the same
IL141822A (en) A method and system for imitating a 3D audio environment
US10757522B2 (en) Active monitoring headphone and a method for calibrating the same
US10582325B2 (en) Active monitoring headphone and a method for regularizing the inversion of the same
CN111556425B (zh) 一种扬声器虚拟声重放的音色均衡方法
Steffens et al. The role of early and late reflections on perception of source orientation
Lee et al. HRTF measurement for accurate sound localization cues
US11653163B2 (en) Headphone device for reproducing three-dimensional sound therein, and associated method
EP0975201A2 (de) Verfahren zur Mehrkanal-Tonsignalverarbeitung
WO2023010691A1 (zh) 一种耳机虚拟空间声回放方法、装置、存储介质及耳机
Pollack Specification of sound-pressure levels
US11044552B2 (en) Acoustic radiation control method and system
Tannaka et al. Correlations between sound field characteristics and subjective ratings on reproduced music sound quality
Griesinger Accurate reproduction of binaural recordings through individual headphone equalization and time domain crosstalk cancellation
Wei et al. Localization of Virtual Sound Source Reproduced by the Crosstalk Cancellation System Under Different Reflective Conditions
Lopez et al. Equalization zones for cross-talk cancellation as a function of loudspeaker position and room acoustics
Sunder et al. Modeling distance-dependent individual head-related transfer functions in the horizontal plane using frontal projection headphones
Tan et al. Method for increasing lateral perceived azimuth of binaural reproduction over two loudspeakers
Masiero Source positioning in a two listener crosstalk cancellation system
Hiekkanen Paikkariippumaton menetelmä kaiuttimien vertailuun
KR19990088677A (ko) 선착효과및반사음을이용한스테레오음상확대회로및방법

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE

AX Request for extension of the european patent

Free format text: AL;LT;LV;MK;RO;SI

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: CREATIVE TECHNOLOGY LTD.

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Kind code of ref document: A3

Designated state(s): AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE

AX Request for extension of the european patent

Extension state: AL LT LV MK RO SI

AKX Designation fees paid

Designated state(s): DE FR GB NL

17P Request for examination filed

Effective date: 20060207

17Q First examination report despatched

Effective date: 20060717

APBK Appeal reference recorded

Free format text: ORIGINAL CODE: EPIDOSNREFNE

APBN Date of receipt of notice of appeal recorded

Free format text: ORIGINAL CODE: EPIDOSNNOA2E

APBR Date of receipt of statement of grounds of appeal recorded

Free format text: ORIGINAL CODE: EPIDOSNNOA3E

APBV Interlocutory revision of appeal recorded

Free format text: ORIGINAL CODE: EPIDOSNIRAPE

GRAP Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOSNIGR1

GRAS Grant fee paid

Free format text: ORIGINAL CODE: EPIDOSNIGR3

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE FR GB NL

REG Reference to a national code

Ref country code: GB

Ref legal event code: FG4D

REG Reference to a national code

Ref country code: DE

Ref legal event code: R096

Ref document number: 69944696

Country of ref document: DE

Effective date: 20130606

REG Reference to a national code

Ref country code: NL

Ref legal event code: T3

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed

Effective date: 20140113

REG Reference to a national code

Ref country code: DE

Ref legal event code: R097

Ref document number: 69944696

Country of ref document: DE

Effective date: 20140113

REG Reference to a national code

Ref country code: FR

Ref legal event code: PLFP

Year of fee payment: 18

REG Reference to a national code

Ref country code: FR

Ref legal event code: PLFP

Year of fee payment: 19

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 20170726

Year of fee payment: 19

REG Reference to a national code

Ref country code: FR

Ref legal event code: PLFP

Year of fee payment: 20

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 20180726

Year of fee payment: 20

Ref country code: DE

Payment date: 20180727

Year of fee payment: 20

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 20180727

Year of fee payment: 20

REG Reference to a national code

Ref country code: NL

Ref legal event code: MM

Effective date: 20180801

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20180801

REG Reference to a national code

Ref country code: DE

Ref legal event code: R071

Ref document number: 69944696

Country of ref document: DE

REG Reference to a national code

Ref country code: GB

Ref legal event code: PE20

Expiry date: 20190711

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF EXPIRATION OF PROTECTION

Effective date: 20190711