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Avoiding Frequency Cancellation Using Multiple Microphones in a Surveillance Camera

Ringsmose, Victoria LU (2021) EITM01 20211
Department of Electrical and Information Technology
Abstract
In surveillance it is important that the recordings are accurate and in as high
quality as possible. The surveillance surroundings and equipment can alter and
change the audio and needs to be compensated for.
This master thesis project investigates whether using multiple microphones
could improve the audio quality. The project was limited to only use analog
electronics and constricted itself to the audible frequency range of 20 Hz to 20
kHz.
The projects started with a theoretical study of different concepts of multiple
microphones, then one concept was implemented and evaluated. The chosen
concept was how to avoid destructive interference using multiple microphones
achieving a frequency response without cancelled frequencies.
... (More)
In surveillance it is important that the recordings are accurate and in as high
quality as possible. The surveillance surroundings and equipment can alter and
change the audio and needs to be compensated for.
This master thesis project investigates whether using multiple microphones
could improve the audio quality. The project was limited to only use analog
electronics and constricted itself to the audible frequency range of 20 Hz to 20
kHz.
The projects started with a theoretical study of different concepts of multiple
microphones, then one concept was implemented and evaluated. The chosen
concept was how to avoid destructive interference using multiple microphones
achieving a frequency response without cancelled frequencies.
After the prestudy, the concept was realised by filtering the signals from two
microphones that were exposed to destructive interference in different frequency
ranges. The filter was based on the Linkwitz-Riley crossover filter.
Simulations were used to evaluate the filter, witch was then realised in a prototype
that was tested in an audio lab.
The test result showed that the concept functioned successfully. The filter
produced a signal without the frequency losses that each of the microphones experienced. (Less)
Please use this url to cite or link to this publication:
author
Ringsmose, Victoria LU
supervisor
organization
course
EITM01 20211
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Audio, analog electronics, acoustics, interferense, cancelled frequencies, surveillance, multiple microphones, frequency analysis, crossover filter, analog filter
report number
LU/LTH-EIT 2021-808
language
English
id
9043399
date added to LUP
2021-05-05 10:33:45
date last changed
2021-05-05 10:33:45
@misc{9043399,
  abstract     = {{In surveillance it is important that the recordings are accurate and in as high
quality as possible. The surveillance surroundings and equipment can alter and
change the audio and needs to be compensated for.
This master thesis project investigates whether using multiple microphones
could improve the audio quality. The project was limited to only use analog
electronics and constricted itself to the audible frequency range of 20 Hz to 20
kHz.
The projects started with a theoretical study of different concepts of multiple
microphones, then one concept was implemented and evaluated. The chosen
concept was how to avoid destructive interference using multiple microphones
achieving a frequency response without cancelled frequencies.
After the prestudy, the concept was realised by filtering the signals from two
microphones that were exposed to destructive interference in different frequency
ranges. The filter was based on the Linkwitz-Riley crossover filter.
Simulations were used to evaluate the filter, witch was then realised in a prototype
that was tested in an audio lab.
The test result showed that the concept functioned successfully. The filter
produced a signal without the frequency losses that each of the microphones experienced.}},
  author       = {{Ringsmose, Victoria}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Avoiding Frequency Cancellation Using Multiple Microphones in a Surveillance Camera}},
  year         = {{2021}},
}