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Room Low Frequency Response Estimation using Microphone Averaging

Room Low Frequency Response Estimation using Microphone Averaging
Room Low Frequency Response Estimation using Microphone Averaging
Little has been published about the repercussions of different source locations and measuring positions for the Low-Frequency Effects (LFE) loudspeakers in cinemas and dubbing theatres (cinema sound-track mixing rooms). The aim of this study is to determine the effects of the number and positioning of the loudspeakers on the uniformity of the response over the listening area, and to assess the effect of the measuring of those responses by the choices made regarding the positioning of the microphones within typically used arrays. Some organizations issuing
recommendations for the installation layout specification, such as Dolby, [1] have long suggested that the installation of low frequency effects loudspeakers below the screen should be made asymmetrically. The reason given for this is to avoid the symmetrical driving of the low-frequency
modal responses of the rooms. If two loudspeakers or groups of loudspeakers are used, one may typically be centred about 20% of the distance fromone side-wall, with the other centred about 33% of the distance from the opposite side wall. However, other organisations, and many designers,
have recommended the mounting of the LFE loudspeakers in tight-packed clusters. Furthermore, it has long been suggested that a single microphone position is inadequate for measuring the response of an LFE channel because the long wavelengths involved make spacial variation in the measurements inevitable. Typically, 4, 5, 8 and 10-microphone arrays have been used, but as rooms differ so much in size, shape and acoustic properties, no universal instructions exist about precisely how to place the microphones in such arrays. This paper examines how the choice of low-frequency source positions and the microphone positions in the common, 5-microphone array can affect the measured average responses over the delineated listening areas. It also discusses how the positioning of the loudspeakers can affects the
evenness of coverage. The results of the spacially averaged responses will be compared with the responses at individual microphone positions, in order to assess how representative the averages are of the responses at specific locations.
Institute of Acoustics
Newell, Julius
abeabf3d-8019-44b8-ab8a-28845cdbc736
Newell, Philip
d2f67626-8c98-4894-a64d-3bf0b5badbbc
Holland, Keith
90dd842b-e3c8-45bb-865e-3e7da77ec703
Newell, Julius
abeabf3d-8019-44b8-ab8a-28845cdbc736
Newell, Philip
d2f67626-8c98-4894-a64d-3bf0b5badbbc
Holland, Keith
90dd842b-e3c8-45bb-865e-3e7da77ec703

Newell, Julius, Newell, Philip and Holland, Keith (2014) Room Low Frequency Response Estimation using Microphone Averaging. In Reproduced Sound 2014. vol. 36, Institute of Acoustics..

Record type: Conference or Workshop Item (Paper)

Abstract

Little has been published about the repercussions of different source locations and measuring positions for the Low-Frequency Effects (LFE) loudspeakers in cinemas and dubbing theatres (cinema sound-track mixing rooms). The aim of this study is to determine the effects of the number and positioning of the loudspeakers on the uniformity of the response over the listening area, and to assess the effect of the measuring of those responses by the choices made regarding the positioning of the microphones within typically used arrays. Some organizations issuing
recommendations for the installation layout specification, such as Dolby, [1] have long suggested that the installation of low frequency effects loudspeakers below the screen should be made asymmetrically. The reason given for this is to avoid the symmetrical driving of the low-frequency
modal responses of the rooms. If two loudspeakers or groups of loudspeakers are used, one may typically be centred about 20% of the distance fromone side-wall, with the other centred about 33% of the distance from the opposite side wall. However, other organisations, and many designers,
have recommended the mounting of the LFE loudspeakers in tight-packed clusters. Furthermore, it has long been suggested that a single microphone position is inadequate for measuring the response of an LFE channel because the long wavelengths involved make spacial variation in the measurements inevitable. Typically, 4, 5, 8 and 10-microphone arrays have been used, but as rooms differ so much in size, shape and acoustic properties, no universal instructions exist about precisely how to place the microphones in such arrays. This paper examines how the choice of low-frequency source positions and the microphone positions in the common, 5-microphone array can affect the measured average responses over the delineated listening areas. It also discusses how the positioning of the loudspeakers can affects the
evenness of coverage. The results of the spacially averaged responses will be compared with the responses at individual microphone positions, in order to assess how representative the averages are of the responses at specific locations.

Text
JN_PN_KH RS2014 - Accepted Manuscript
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More information

Published date: 15 October 2014
Venue - Dates: Institute of Acoustics - Reproduced Sound 2014, 2014-10-14 - 2014-10-15
Organisations: Acoustics Group

Identifiers

Local EPrints ID: 410278
URI: http://eprints.soton.ac.uk/id/eprint/410278
PURE UUID: dd954370-e2c1-4f60-b337-becaed5bd9c9
ORCID for Keith Holland: ORCID iD orcid.org/0000-0001-7439-2375

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Date deposited: 06 Jun 2017 04:04
Last modified: 15 Mar 2024 13:43

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Contributors

Author: Julius Newell
Author: Philip Newell
Author: Keith Holland ORCID iD

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