1. Objective and Subjective Audio Assessment of MP3 Players’ Quality
E6820 Project Proposal
Objective and Subjective Audio Assessment of MP3 Players’ Quality

2. Objective: Evaluate and compare the quality of MP3 players partly based on International Telecommunication Union (ITU) recommendation called PEAQ.
Motive 1: Formal listening tests are time consuming. Therefore it is of interest to identify how much of this process can be performed successfully by the much faster objective measurement method.
Motive 2: It is important to be able to correlate and scientifically report what we hear.

3. PEAQ
PEAQ: (Perceptual Evaluation of Audio Quality) method, which is based on a generally accepted psychoacoustic principles, predict and correlate the results of subjective tests objectively.
The model processes the two audio signals to be compared (namely the original reference signal and an impaired version to be evaluated) and calculates instantaneously a quality rating similar to the mean rating that would be obtained if a formal subjective test were conducted.
OPTICON one of the joint developers of PEAQ standard has come up with a software that objectively evaluate and assure the quality of compressed speech and audio signals.

4. An example of the performance of this method may be seen in the accompanying figures where objective codec
quality measurements are compared with corresponding subjective ratings.

5. Take a “PEAQ” at My Project
Run subjective tests with selected audio materials for different codecs.
The quality of the compressed test signal (different mp3 codecs) will be measured relative to the reference signal (CD quality).
Audio materials should have characteristics, which will challenge the codecs ability to encode and decode such as tonality and high frequency content.
Rate from 1-5 scale.
Develop objective algorithm to correlate with subjective tests based on a few audio characteristics.

6. Possible Features to Extract
Signal Bandwidth: audio codecs often limit the bandwidth of coded signals. Such truncation alters the perceived timbre and signals may sound dull or muffled.
Loudness of distortions: takes into account the reduction in perceived loudness of an audible distortion due to the masker.
Harmonic structure
Noise-to-mask ratio (NMR): describes the difference in dB between signal-to-mask ratio and SNR to be expected from quantization. Coding noise will not be audible as long as NMR is negative.