An Overview of Delay-and-sum Beamforming DSP Seminar (1st semester, 2006 - 2007) An Overview of Delay-and-sum Beamforming Student: Wong Hok Him Supervisor: Professor P.C. Ching Date: 11th January, 2007

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

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

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)

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

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

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

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

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

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

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

Delay-and-sum Beamforming (1)

Delay-and-sum Beamforming (2)

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

Delay-and-sum Beamforming (4)

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

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

Q & A Thank You!