Perceptual Evaluation of Speech Quality (PESQ)

PESQ is a family of standards including a test methodology for automated objective assessment of the speech quality
to replace the jury test (a group of listeners). It is standardized as ITU-T recommendation P.862. Nowadays, PESQ is
a worldwide applied industry standard for objective voice quality testing used bycommunication peripheral terminal
products, phone manufacturers, and network equipment vendors. PESQ is the result of many years of development
and is applicable not only to speech codecs but also to end-to end measurements.
Overview of the basic philosophy
PESQ compares an “original input signal” with a “degraded output” that is the result of passing through a DUT (or a
communication system). The output of PESQ is to quantify the difference between the “ideal model” and the “degraded
output”. It also represents the result in a subjective listening test.
The calculation of PESQ is achieved in several stages
    1.      Time alignment
    2.      Level alignment to a calibrated listening level
    3.      Time-frequency mapping
    4.      Frequency warping,
    5.      Compressive loudness scaling
The following table shows the main standards for evaluating PESQ. Nowadays, ITU-T Recommendation P.862.2 is the
most popular one for PESQ measurement. It is an extension standard of ITU-T Recommendation P.862 specialized for
wideband telephone network and speech codecs.
Test Contents
According to ITU-T Recommendation P.862, the PESQ test should include the following contents: 5 languages,
2 Genders, and 4 different speech sections. Therefore, totally 40 measurements should be evaluated.
How to score?
PESQ uses Mean Opinion Score (MOS) to evaluate the speech quality. The MOS is expressed as a single
number in the range of 1 to 5, where 1 is the lowest score, and 5 is the highest one. It is the arithmetic mean
of all individual scores. Generally, if the MOS is higher than 4.0, the users will feel satisfied.
Factors to affect PESQ score
There are many factors will affect PESQ score, such as:

   1. Codec distortion

   2. Packet delay and loss

   3. Jitter butter delay

   4. Background noise

   5. Others...

For PAL’s measurement, we assume the quality of internet is perfect, that means no packet loss, constant
delay, and no background noise interference. We just focus on the speech quality degraded by the DUT.
Of course, if you want to evaluate the speech quality in the impaired internet environment, we also can
provide this service.


Contact with PAL
If you are interested in the service or want more information, you can contact with our sales representative
by phone or e-mail:
  E-mail: sales@pal-acoustics.com
  Tel: 886-2-26272515