Measurement of signal quality

A method according to clam 5, in which the quality of each received test signal Y′C is derived according to the formula:

• ln ⁢ ⁢ ( Y C ′ 4 - Y C ′ ) = 0.7 ⁢ [ ln ⁢ ⁢ ( Y LE 4 - Y LE ) + 0.5 - ( K × 13 - STMR ) 20 ) ⁢ ( 4 - Y LE Y LE ) 2 ]
• where
• K=1 if STMR<13
• K=0 otherwise,
• YLE is the measured listening effort of the received signal, and
• STMR is the Sidetone Masking Rating value generated by the customer equipment interface simulator.

Apparatus for testing telecommunications equipment over which two-way speech traffic can be carried between a first test point and a second test point, the apparatus comprising:

• means for generating first and second test signals representative of normal conversation, each having a predetermined vocal level;
• means for supplying the first test signal to the first test point for transmission to the second test point;
• means for detecting at the first test point a signal received from the second test point;
• means for measuring the quality of the detected signal by comparison with the second test signal, using a perceptual analysis process in which the extent is measured to which the received signals carry distortions which would be perceptible to a human listener;
• means for determining a vocal level adjustment to be made in response to the measured quality;
• means for adjusting the vocal level of the first test signal until a predetermined condition is reached;
• and
• means for generating an output indicative of the quality measured when said predetermined condition is reached;
• wherein between the test apparatus and telecommunications equipment is interposed a customer equipment interface simulator which simulates the modifications to a signal which occur between a talker and the telecommunications equipment under test, and between the telecommunications equipment under test and the listener;
• and in which the customer equipment interface simulator includes means for modelling the effects of sound leakage in a telephone user/equipment interface.

Apparatus for testing telecommunications equipment over which two-way speech traffic can be carried between a first test point and a second test point, the apparatus comprising:

• means for generating first and second test signals representative of normal conversation, each having a predetermined vocal level;
• means for supplying the first test signal to the first test point for transmission to the second test point;
• means for detecting at the first test point a signal received from the second test point;
• means for measuring the quality of the detected signal by comparison with the second test signal, using a perceptual analysis process in which the extent is measured to which the received signals carry distortions which would be perceptible to a human listener;
• means for determining a vocal level adjustment to be made in response to the measured quality;
• means for adjusting the vocal level of the first test signal until a predetermined condition is reached;
• and
• means for generating an output indicative of the quality measured when said predetermined condition is reached;
• wherein between the test apparatus and telecommunications equipment is interposed a customer equipment interface simulator which simulates the modifications to a signal which occur between a talker and the telecommunications equipment under test, and between the telecommunications equipment under test and the listener;
• and the customer equipment interface simulator has means for generating a noise signal for combining with the respective test signal, the noise signal being modified in accordance with the frequency response of a microphone, to simulate the sensitivity of the microphone to ambient noise.

The combination of two apparatuses, each apparatus for testing telecommunications equipment over which two-way speech traffic can be carried between a first test point and a second test point, each apparatus comprising:

• means for generating first and second test signals representative of normal conversation, each having a predetermined vocal level;
• means for supplying the first test signal to the first test point for transmission to the second test point;
• means for detecting at the first test point a signal received from the second test point;
• means for measuring the quality of the detected signal by comparison with the second test signal, using a perceptual analysis process in which the extent is measured to which the received signals carry distortions which would be perceptible to a human listener;
• means for determining a vocal level adjustment to be made in response to the measured quality;
• means for adjusting the vocal level of the first test signal until a predetermined condition is reached;
• means for generating an output indicative of the quality measured when said predetermined condition is reached;
• and
• the combination being for connection to respective first and second test points of a telecommunications equipment, and both arranged to generate the same first and second test signals, and to supply respectively the first and second signals to their respective test points, for transmission to the respective other test point, and to compare the signal received at the respective test point with the second and first test signals respectively.

Apparatus for testing telecommunications equipment over which two-way speech traffic can be carried between a first test point and a second test point, the apparatus comprising:

• means for generating first and second test signals representative of normal conversation, each having a predetermined vocal level;
• means for supplying the first test signal to the first test point for transmission to the second test point;
• means for detecting at the first test point a signal received from the second test point;
• means for measuring the quality of the detected signal by comparison with the second test signal, using a perceptual analysis process in which the extent is measured to which the received signals carry distortions which would be perceptible to a human listener;
• means for determining a vocal level adjustment to be made in response to the measured quality;
• means for adjusting the vocal level of the first test signal until a predetermined condition is reached;
• means for generating an output indicative of the quality measured when said predetermined condition is reached;
• and
• means for simulating a conversation comprising:
• a store for storing a plurality of speech segments forming a conversation;
• a receiver for receiving speech segments from one or more complementary devices,
• a comparison device for comparing speech segments received by the receiver with speech segments stored in the store;
• selection means responsive to the comparison device for selecting from the store a speech segment for transmission to the complementary device or devices, in accordance with the content and quality of the received speech segments;
• and
• transmission means for transmitting a speech segment selected by the selection means to the complementary device or devices.