Telephone instrument and method for altering audible characteristics

DETAILED DESCRIPTION It is an object of the present invention to provide a telephone instrument and method for altering a voice signal received from a telephone line to simulate a characteristic of spatial presence.
According to one aspect of the present invention, there is provided a telephone instrument for receiving signals from and for transmitting signals to another telephone instrument via a telephone line, the telephone instrument comprising: transmitter means; a pair of receiver means for use in acoustical association with the left and right ears of a user of the telephone instrument; signal coupling means including signal transmitting means and signal receiving means, the signal transmitting means transmitting signals from the transmitter means to the telephone line and coupling the received signals; and a pair of received signal processing means, each receiving the respective received signal X(i), each received signal processing means including direct path processing means, finite impulse processing means, all-pass signal means and signal summing means.
The direct path processing means processes the received signal X(i) and provides a direct path output signal which is proportional to the received signal X(i); the finite impulse processing means processes the received signal X(i) and provides a finite impulse output signal which is proportional to .
SIGMA.
C(k) X(i-k); the all-pass signal means processes the finite impulse output signal and provides an all-pass output signal which is proportional to .
beta.
(i-M), where .
beta.
(i)=(-g).
multidot.
X(i)+(1-g.
sup.
2).
multidot.
.
alpha.
(i-N), and .
alpha.
(i)=X(i)+g.
multidot.
.
alpha.
(i-N), wherein, C(k) represents a sequence of finite impulse response coefficients, g is a gain coefficient, and M and N represent delay coefficients.
The signal summing means sums the direct path output signal, the finite impulse output signal and the all-pass output signal and provides a summed signal for operation of the respective one of the pair of receiver means