Transcript Document

Audio System
Measurement and
Improvement
Group 10
Advisor Jaijeet Roychowdhury
Team Mohamud Ismail
Franklin Wong
Andrew Johnson
Garett Kauer
Outline
Purpose
 Solution
 Requirements / Specs
 Budget / Timeline
 Conclusion

Purpose
Turn Cheap Dell A225
PC Speakers
Into speakers comparable to
much more expensive
speakers with an easy to
use device that has a low
consumer cost
http://www.techexcess.net/images/pr
oducts/Dell/dell-a225.jpg
http://www.theage.com.au/ffximage/bose
_wideweb__470x367,2.jpg
Quick Explanation in Frequency Analysis
Frequency Response of Speakers
0
-20
-40
-60
dB
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-100
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2
10
3
10
frequency (Hz)
http://www.carstereohelp.com/images/PontiacStrMonsoon06280201.jpg
4
10
Our Solution
Computer
Speaker
Microphone
Feedback
Known Spectrum
Unknown spectrum
Known after processing
Our Solution
Frequency
Frequency
Frequency
Frequency
Response
Response
Response
Response
ofofwhite
ofwhite
ofwhite
white
noise
noise
noise
noise
Frequency
Frequency
Frequency
Frequency
Response
Response
Response
Response
ofofSpeakers
ofSpeakers
ofSpeakers
SpeakersFrequency
Frequency
Frequency
Frequency
Response
Response
Response
Response
ofofRoom
ofRoom
ofRoom
Room
Frequency
Frequency
Frequency
Frequency
Response
Response
Response
Response
ofofMicrophone
ofMicrophone
ofMicrophone
Microphone
00 0 0
00 0 0
00 0 0
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dB
dB
dB
dB
00 0 0
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frequency
frequency
frequency
frequency
(Hz)
(Hz)
(Hz)
(Hz)
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frequency
frequency
frequency
frequency
(Hz)
(Hz)
(Hz)
(Hz)
Frequency Response of Entire System
80
-20
60
Entire System after precoding
0
-20
-40
dB
-40
frequency
frequency
frequency
frequency
(Hz)
(Hz)
(Hz)
(Hz)
Inverse Response
100
0
-60
-60
-60
-60
frequency
frequency
frequency
frequency
(Hz)
(Hz)
(Hz)
(Hz)
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-100
frequency (Hz)
-60
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http://www.copystars.com/images_products/shure_pgx24pg58_s19016.jpg
frequency (Hz)
frequency (Hz)
http://blog.audiovideointeriors.com/1206mountain.1.jpg
Software Design

What Software Does
 Measurement

System
Measures, Displays and Compares Transfer
Functions
 De-embedding/Correction
System
Generates Inverse Transfer Function
 Precodes Output


Done Using ALSA
Software Design

Specifications To Meet
 Measurement

System
Greater than 20dB of relative nulling over 1-5kHz
 De-embedding/Correction
System
Corrected transfer function
 Flat to within 5dB over 100Hz-10kHz

Software Design

ALSA
 Advanced
Linux Sound Architecture
 Provides audio and MIDI functionality to Linux
 Handles Sound Device Drivers
 User Space Library
Simple Application Programming
 Provides High Level Functionality

Software Design

ALSA
 Efficient
support for all types of sound devices
 Fully modularized sound drivers
 Thread-safe design
 Supports Open Sound System (OSS)
Software development will be open source,
created to operate using a Linux system. Project
software will comprise two separate systems.
The first will be used to measure the audio
response within a room by interfacing with a
microphone. The second system will be used to
correct the speaker output to adjust for linear
Microphone Selection
Graphic provided by Shure Incorporated www.shure.com
“Performance Gear Microphone Guide”
Selection Considerations
Frequency Response
 Range of Reception
 Ease of Use
 Durability
 Cost

Frequency Response
Relative Frequency Response
Response in dB
20
10
0
-10
-20
-30
1
10
100
1000
10000
100000
Frequency in Hz
Ideal Response
Response provided by Shure Incorporated www.shure.com
“Performance Gear Microphone Guide”
Shure PG58 Response
Range of Response
Reception at <15cm
 Direct proximity to Microphone head
 Simulates Ear perception

Budget
Quantity Item
Price
1 PC with Speakers (provided)
1 Shure PG58 microphone
Total
$0.00
$69.95
$69.95
Timeline
Complete
In Progress
In Conclusion…


Frequency
Frequency
Response
Response
of Entire
of Entire
System
System
0
Inverse
Inverse
Response
Response
100 100
0
-20 -20
-40 -40
80
80
60
60
40
40
20
20
0
0
Entire
Entire
System
System
after after
precoding
prec
0
0
-20 -20
-40 -40
dB

Want to improve cheap
speakers
Correct the distortion
inherent in room and
speakers
End-user needs only
software and a microphone
Software should be free and
easy to use
dB

-60 -60
-80 -80
-100 -100
frequency
frequency
(Hz) (Hz)
-60 -60
-80 -80
-100 -100
frequency
frequency
(Hz) (Hz)
http://www.popculturecomics.com/graphics
frequency
frequency
(Hz) (Hz)
Project Future




Created software
distributed as opensource, but…
Load software onto
small self-contained
device
No PC needed
Commercial potential
Calibrate Button
Line Out
Audio Input
Microphone
Questions?