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Audio System Measurement and Improvement
Group 10Advisor Jaijeet Roychowdhury
Team Mohamud Ismail
Franklin Wong
Andrew Johnson
Garett Kauer
Outline
Purpose Solution Requirements / Specs Budget / Timeline Conclusion
Purpose
http://www.techexcess.net/images/products/Dell/dell-a225.jpg
http://www.theage.com.au/ffximage/bose_wideweb__470x367,2.jpg
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
Quick Explanation in Frequency Analysis
http://www.carstereohelp.com/images/PontiacStrMonsoon06280201.jpg
102
103
104
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-80
-60
-40
-20
0Frequency Response of Speakers
frequency (Hz)
dB
Our Solution
Speaker MicrophoneComputer
Feedback
Known Spectrum
Unknown spectrum
Known after processing
Our Solution
-100
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-60
-40
-20
0
Frequency Response of Entire System
frequency (Hz)
dB
0
20
40
60
80
100Inverse Response
frequency (Hz)-100
-80
-60
-40
-20
0
Entire System after precoding
frequency (Hz)
-60
-50
-40
-30
-20
-10
0
Frequency Response of white noise
frequency (Hz)
dB
-60
-50
-40
-30
-20
-10
0
Frequency Response of Speakers
frequency (Hz)-60
-50
-40
-30
-20
-10
0
Frequency Response of Room
frequency (Hz)-60
-50
-40
-30
-20
-10
0
Frequency Response of Microphone
frequency (Hz)
-100
-80
-60
-40
-20
0
Frequency Response of Entire System
frequency (Hz)
dB
0
20
40
60
80
100Inverse Response
frequency (Hz)-100
-80
-60
-40
-20
0
Entire System after precoding
frequency (Hz)
-60
-50
-40
-30
-20
-10
0
Frequency Response of white noise
frequency (Hz)
dB
-60
-50
-40
-30
-20
-10
0
Frequency Response of Speakers
frequency (Hz)-60
-50
-40
-30
-20
-10
0
Frequency Response of Room
frequency (Hz)-60
-50
-40
-30
-20
-10
0
Frequency Response of Microphone
frequency (Hz)-60
-50
-40
-30
-20
-10
0
Frequency Response of white noise
frequency (Hz)
dB
-60
-50
-40
-30
-20
-10
0
Frequency Response of Speakers
frequency (Hz)-60
-50
-40
-30
-20
-10
0
Frequency Response of Room
frequency (Hz)-60
-50
-40
-30
-20
-10
0
Frequency Response of Microphone
frequency (Hz)-60
-50
-40
-30
-20
-10
0
Frequency Response of white noise
frequency (Hz)
dB
-60
-50
-40
-30
-20
-10
0
Frequency Response of Speakers
frequency (Hz)-60
-50
-40
-30
-20
-10
0
Frequency Response of Room
frequency (Hz)-60
-50
-40
-30
-20
-10
0
Frequency Response of Microphone
frequency (Hz)
-100
-80
-60
-40
-20
0
Frequency Response of Entire System
frequency (Hz)
dB
0
20
40
60
80
100Inverse Response
frequency (Hz)-100
-80
-60
-40
-20
0
Entire System after precoding
frequency (Hz)
http://blog.audiovideointeriors.com/1206mountain.1.jpg
http://www.copystars.com/images_products/shure_pgx24pg58_s19016.jpg
Software Design
What Software DoesMeasurement System
Measures, Displays and Compares Transfer Functions
De-embedding/Correction System Generates Inverse Transfer Function Precodes Output
Done Using ALSA
Software Design
Specifications To MeetMeasurement 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
ALSAAdvanced Linux Sound ArchitectureProvides audio and MIDI functionality to LinuxHandles Sound Device DriversUser 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 non-idealities produced by the audio system and room acoustics.
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
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-10
0
10
20
1 10 100 1000 10000 100000
Frequency in Hz
Resp
on
se i
n d
B
Ideal Response Shure PG58 Response
Response provided by Shure Incorporated www.shure.com
“Performance Gear Microphone Guide”
Range of Response
Reception at <15cm Direct proximity to Microphone head Simulates Ear perception
Budget
Quantity Item Price
1 PC with Speakers (provided) $0.00
1 Shure PG58 microphone $69.95
Total $69.95
TimelineTask Name Start Finish
Audio Enhancement Device 1/28/2008 5/13/2008get linux box up and running 1/28/2008 2/15/2008find and purchase microphone 2/4/2008 2/29/2008link microphone and PC 3/3/2008 3/7/2008implement Xfer Fn finder/invertor 3/10/2008 3/14/2008link transfer function to ALSA 3/17/2008 3/21/2008test 3/24/2008 4/4/2008create user friendly UI 4/7/2008 4/11/2008prepare final prototype 4/14/2008 4/25/2008buffer 4/28/2008 5/13/2008
E B M E B M E B M E B M EJanuary February March April May
Complete
In Progress
In Conclusion…
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
-100
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-60
-40
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0
Frequency Response of Entire System
frequency (Hz)
dB
0
20
40
60
80
100Inverse Response
frequency (Hz)-100
-80
-60
-40
-20
0
Entire System after precoding
frequency (Hz)-100
-80
-60
-40
-20
0
Frequency Response of Entire System
frequency (Hz)
dB
0
20
40
60
80
100Inverse Response
frequency (Hz)-100
-80
-60
-40
-20
0
Entire System after precoding
frequency (Hz)
http://www.popculturecomics.com/graphics
Project Future
Created software distributed as open- source, but…
Load software onto small self-contained device
No PC needed Commercial potential
Calibrate Button
MicrophoneLine Out
Audio Input
Questions?