Microphone Array Project

ECE5525 – Speech Processing

Robert Villmow12/11/03

Microphone Array Purpose

Microphone Array Purpose• Improves sound reception when interfering

sources are located far enough apart • spatial separation

• Capable of determinig the direction a sound is coming from

Background

Data sampled at each microphone is different due to different angles of arrival

Delay and Sum Algorithm• Assume a sound is arriving at a specific angle then calculate

when that sound will be sampled by the other microphones

• Sound arriving from desired angle will be correlated between microphones

• Sound arriving from other angles will be uncorrelated

• Summation of the data will attenuate uncorrelated signals

15 Element Microphone Array

High

Middle

Low

Low Array• 4x spacing as high array

Middle Array• 2x spacing as high array

High Array• minimum spacing between microphones

Microphone Sampling

Source at 10°

Source at 50°Source at 90°

Source at 0°

Sampling Summary

Sample rate affects performance• sampled data differs between microphones

• algorithm depends on data being correlated between microphonesS

Sound sources at 0° are not affected by sample rate• sampled by all microphones at the same time

High Array

Low Frequency Response• Similar to a single microphone

High Frequency Response• Narrow beam width

Frequency Responses at 4400 Hz

Low Array

Low Frequency Response• Good Directional response

High Frequency Response• Too many Grating lobes

Frequency Responses at 800 Hz

Block Diagram

BP FilterHigh Freq

BP FilterMiddle Freq

BPFilterLow Freq

2.5khz – 4.5khz

1.5khz – 2.5khz

300hz – 1.5khz

Array Test Configuration

Speaker

Radio

45°

CMU Microphone Array Data

15 Channels 16 kHz, 16-bit linear Sampling Files used

• an101-mtms-arr3A.adc• 3 cm spacing in a noisy computer lab

• Speaker is 1 meter from array

• an101-mtms-arr4A.adc• 4 cm spacing in a noisy computer lab

• Speaker is 1 meter from array

• an101-mtms-arrCR1A.adc• 4 cm spacing with radio at 45°

• Speaker at a distance of 1 meters

-100 -80 -60 -40 -20 0 20 40 60 80 1002.5

3

3.5

4x 10

4 Maximum Peak Error - Summed vs. Single Channel

-100 -80 -60 -40 -20 0 20 40 60 80 1000.5

1

1.5

2

2.5

3

3.5x 10

7 Mean Squared Error - Summed vs. Single Channel

-100 -80 -60 -40 -20 0 20 40 60 80 1002.5

3

3.5

4x 10

4 Maximum Peak Error - Summed vs. Single Channel

-100 -80 -60 -40 -20 0 20 40 60 80 1001

1.5

2

2.5

3

3.5x 10

7 Mean Squared Error - Summed vs. Single Channel

-100 -80 -60 -40 -20 0 20 40 60 80 1002

3

4

5

6x 10

4 Maximum Peak Error - Summed vs. Single Channel

-100 -80 -60 -40 -20 0 20 40 60 80 1000.5

1

1.5

2

2.5

3

3.5x 10

7 Mean Squared Error - Summed vs. Single Channel

Arr3A Results

Difference – Single Channel vs. Summed signal

Mean Squared Error – Single Channel vs. Summed signal

High Middle Low

Arr3A – Mean Squared Error

Array Max Min

High 9.8070 x 106 3.3647 x 107

Middle 1.0517 x 107 3.4093 x 107

Low 7.7878 x 106 3.1970 x 107

-100 -80 -60 -40 -20 0 20 40 60 80 1002

2.5

3

3.5

4x 10

4 Maximum Peak Error - Summed vs. Single Channel

-100 -80 -60 -40 -20 0 20 40 60 80 1000

2

4

6

8x 10

7 Mean Squared Error - Summed vs. Single Channel

-100 -80 -60 -40 -20 0 20 40 60 80 1001.5

2

2.5

3

3.5

4x 10

4 Maximum Peak Error - Summed vs. Single Channel

-100 -80 -60 -40 -20 0 20 40 60 80 1000

2

4

6

8x 10

7 Mean Squared Error - Summed vs. Single Channel

-100 -80 -60 -40 -20 0 20 40 60 80 1002

2.5

3

3.5

4x 10

4 Maximum Peak Error - Summed vs. Single Channel

-100 -80 -60 -40 -20 0 20 40 60 80 1000

2

4

6

8x 10

7 Mean Squared Error - Summed vs. Single Channel

Arr4A Results

Mean Squared Error – Single Channel vs. Summed signal

Difference – Single Channel vs. Summed signal

High Middle Low

Arr4A – Mean Squared Error

Array Max Min

High 8.1192 x 106 6.7789 x 107

Middle 8.3030 x 106 6.8715 x 107

Low 6.3974 x 106 6.7689 x 107

-100 -80 -60 -40 -20 0 20 40 60 80 1002.5

3

3.5

4

4.5x 10

4 Maximum Peak Error - Summed vs. Single Channel

-100 -80 -60 -40 -20 0 20 40 60 80 1004

6

8

10

12

14x 10

6 Mean Squared Error - Summed vs. Single Channel

-100 -80 -60 -40 -20 0 20 40 60 80 1002

2.5

3

3.5

4

4.5x 10

4 Maximum Peak Error - Summed vs. Single Channel

-100 -80 -60 -40 -20 0 20 40 60 80 1004

6

8

10

12

14x 10

6 Mean Squared Error - Summed vs. Single Channel

-100 -80 -60 -40 -20 0 20 40 60 80 1002.5

3

3.5

4x 10

4 Maximum Peak Error - Summed vs. Single Channel

-100 -80 -60 -40 -20 0 20 40 60 80 1004

6

8

10

12

14x 10

6 Mean Squared Error - Summed vs. Single Channel

ArrCR1A Results (Interpolated)

Difference – Single Channel vs. Summed signal

Mean Squared Error – Single Channel vs. Summed signal

ArrCR1A – Mean Squared Error

Array Max Min

High 5.0761 x 106 1.2176 x 107

Middle 5.2716 x 106 1.3283 x 107

Low 4.3089 x 106 1.3238 x 107

Sound Results

Sound Files...

Summary

Microphone array increases SNR Array Response is best at angles between

±30° Oversampling smoothes array response

• increased computations

• decreases performance lost due to sampling