1. An Overview of Delay-and-sum Beamforming
DSP Seminar (1st semester, )
An Overview of Delay-and-sum Beamforming
Student:
Wong Hok Him
Supervisor:
Professor P.C. Ching
Date:
11th January, 2007

2. Outline Objective Introduction Delay-and-sum Beamforming Future Works
Q & A

3. Objective
Design a small-dimensional microphone array for beamforming in an acoustic environment with the presence of noises

4. Introduction (1) Microphone
Characterized by a spatial directivity pattern, which specifies the gain and phase shift that the microphone gives to a signal coming from a certain direction (angle-of-arrival)

5. Introduction (2) Spatial directivity pattern
Function of angle-of-arrival and frequency
Transfer function for source of a particular frequency  at angle 

6. Introduction (3) Spatial filtering
Received signals from different microphones
Filtering
Summing
Spatial filtering
“Virtual” spatial directivity pattern

7. Introduction (4) Spatial filter design is based on two factors
Microphone characteristics
Microphone array configuration

8. Introduction (5) Beamforming Can be thought of as spatial filtering
Can increase the receiver sensitivity in the direction of wanted signals
Can decrease the receiver sensitivity in the direction of interferences and noises

9. Covered in this seminar
Introduction (6)
Two categories of beamforming
Fixed beamforming
Delay-and-sum beamforming
Weighted-sum beamforming
Filter-and-sum beamforming
Adaptive beamforming
LCMV beamforming
Generalized sidelobe canceller
Covered in this seminar

10. Introduction (7)
Basic differences between fixed and adaptive beamforming
Fixed beamforming
Adaptive beamforming
Fixed filters
Adaptive filters
Data-independent
Data-dependent

11. Introduction (8) Assumptions
Microphone gain = 1 at all angles for all frequencies
Far-field source (plane waveforms)

12. Delay-and-sum Beamforming (1)

13. Delay-and-sum Beamforming (2)

14. Delay-and-sum Beamforming (3)
Simulation settings
Number of microphones M = 5
Distance between neighbouring microphones d = 0.03 m
Sampling frequency fs = 16 kHz
Source frequency f = 5000 Hz

15. Delay-and-sum Beamforming (4)

16. Future Works
Investigate into adaptive beamforming, e.g. GSC, which has the ability to minimize noises
Perform simulations to compare the performances of various existing types of adaptive beamforming in a noisy environment

17. Reference
Microphone Array Processing, Marc Moonen, Dept. E.E., EAST, K.U.Leuven

18. Q & A
Thank You!