Apparatus and method for detecting sound direction

1. An apparatus for detecting sound direction, comprising:

a plurality of sound source detecting units, each receiving a sound signal from a sound source, amplifying and filtering the sound signal for generating a amplified sound signal, and then transforming the amplified sound signal to a pulses signal; and

a processing unit, coupled to the sound source detecting units, respectively, for sampling the pulse signals outputted from the sound source detecting units to generate a plurality of sampling signal sequences, and then performing a maximum likelihood method on the sampling signal sequences to obtain a plurality time differences, thereby detecting a position of the sound source via a table look-up method based on the time differences;

wherein the sampling signal sequences are represented as {right arrow over (χ)} 1 , {right arrow over (χ)} 2 , {right arrow over (χ)} 3 ∈{1,0}, the sampling length of the sampling signal sequence sampled by the processing unit is L, and the time differences are represented as Δ 1 , Δ 2 , Δ 3 , where Δ 1 is the time difference between {right arrow over (χ)} 1 and {right arrow over (χ)} 2 , Δ 2 is the time difference between {right arrow over (χ)} 2 and {right arrow over (χ)} 3 , Δ 3 is the time difference between {right arrow over (χ)} 3 and {right arrow over (χ)} 1 ; and the maximum likelihood method is performed as follows:

L(a|x)=f(x|a) for a in A and x in S,

if a=Δ 1 , then x={right arrow over (χ)} 1 (n)·{right arrow over (χ)} 2 (n+Δ 1 ),

if a=Δ 2 , then x={right arrow over (χ)} 2 (n)·{right arrow over (χ)} 3 (n+Δ 2 ),

if a=Δ 3 , then x={right arrow over (χ)} 3 (n)·{right arrow over (χ)} 1 (n+Δ 3 ),

where A is a possible time difference (A∈{0,Δ possible max }) and S∈{1,0}, thereby computing the time differences and maximizing the corresponding L(a|x)=f(x|a).

2. The apparatus as claimed in claim 1 , wherein each sound source detecting unit further comprises a pre-amplifier and a signal detector for transforming the sound signals to the pulse sequences having high transition and low transition.

3. The apparatus as claimed in claim 2 , wherein each sound source detecting unit further comprises a receiver coupled to the pre-amplifier and a post-amplifying and filtering unit coupled to the pre-amplifier, the signal detector being coupled to the post-amplifying and filtering unit and the processing unit, respectively.

4. The apparatus as claimed in claim 2 , wherein each pre-amplifier employs a bipolar junction transistor (BJT) for amplification.

5. The apparatus as claimed in claim 4 , wherein the BJT is a NPN transistor.

6. The apparatus as claimed in claim 2 , wherein each signal detector is a zero crossing detector (ZCD).

7. The apparatus as claimed in claim 2 , wherein the processing unit performs the table look-up method based on an incident angle table having a plurality of predetermined time difference values and a plurality of incident angle, thereby comparing the time differences and the predetermined time difference values to obtain a corresponding incident angle for detecting the source position of the sound signals.

8. A method for detecting sound direction, comprising:

a detection parameter setting step for setting at least one sampling length parameter and one detecting number parameter;

a sound wave signal transforming step for receiving a plurality of sound signals from a sound source and transforming the sound signals to a plurality of pulse signals;

a sampling step for sampling the pulse signals based on the sampling length parameter, and computing a plurality of time differences via a maximum likelihood method; and

a table look-up step for comparing the time differences and a incident angle table to obtain a plurality of sound signal incident angles, thereby detecting the position of the sound source of the sound wave signals based on the sound wave signal incident angles;

wherein the maximum likelihood method includes the following steps:

L(a|x)=f(x|a) for a in A and x in S,

if a=Δ 1 ,then x={right arrow over (χ)} 1 (n)·{right arrow over (χ)} 2 (n+Δ 1 ),

if a=Δ 2 ,then x={right arrow over (χ)} 2 (n)·{right arrow over (χ)} 3 (n+Δ 2 ),

if a=Δ 3 ,then x={right arrow over (χ)} 3 (n)·{right arrow over (χ)} 1 (n+Δ 3 ),

where A is a possible time difference (A∈{0,Δ possible max }) and S∈{1,0}, thereby computing the time differences and maximizing the corresponding L(a|x)=f(x|a), {right arrow over (χ)} 1 , {right arrow over (χ)} 2 , {right arrow over (χ)} 3 ∈{1,0}are sampling signal sequence of the pulse signals, L is the sampling length of the sampling signal sequence sampled by the processing unit, and Δ 1 , Δ 2 , and Δ 3 are the time differences, where Δ 1 is the time difference between {right arrow over (χ)} 1 and {right arrow over (χ)} 2 , Δ 2 is the time difference between {right arrow over (χ)} 2 and {right arrow over (χ)} 3 , and Δ 3 is the time difference between {right arrow over (χ)} 3 and {right arrow over (χ)} 1 .

9. The method as claimed in claim 8 , further comprising an averaging step after the table look-up step, for temporarily storing the sound signal incident angles and performing plural times of the sampling step and the table look-up step based on the detecting parameter for obtaining plural sets of sound signal incident angles to be averaged.

10. The method as claimed in claim 9 , wherein the averaging step excludes the maximum and the minimum of the sound wave signal incident angles.