Apparatus and method for generating low level noise signals

DETAILED DESCRIPTION In accordance with the present invention, apparatus and a method for generating low level noise signals are provided which substantially eliminate or reduce disadvantages and problems associated with prior circuits.
In one aspect of the present invention, a method for generating low level noise signals is provided.
Two random numbers X.
sub.
1 and Y.
sub.
1 are first generated and bits 0-4 of the first random number X.
sub.
1 are extracted to produce a number X.
sub.
2.
A number X.
sub.
3 is further computed by the formula X.
sub.
3 =2.
sup.
-N (X.
sub.
2 .
times.
I), where N is a predetermined number and 1.
ltoreq.
I.
ltoreq.
2.
sup.
N -1.
Bit 7 of the second random number Y.
sub.
1 is then extracted and combined as a sign bit with the computed number X.
sub.
3 to produce a sign-magnitude eight-bit number W representing a sample of low level noise encoded in accordance with .
mu.
-law.
In yet another aspect of the present invention, apparatus for generating low level noise signals is provided which comprises means for generating a random number and for extracting the n least significant bits of the random number.
Additionally, means is further provided for multiplying the extracted n bits by a first predetermined number I and producing a product, and for right shifting the bits of the product by a second predetermined number N places.
A random sign bit is generated and combined with the right shifted bits to produce a noise sample that is in accordance with .
mu.
-law.
An important technical advantage of the present invention provides for a method and apparatus for generating low level noise signals in accordance with .
mu.
-law without the additional hardware, computational power and time required by conventional means.