Audio quality of portable players
As perceived audio quality of portable players depends mostly on performance of their digital and analog hardware circuits, objective audio measurements are important. At SoundExpert such measurements are performed in accordance with the innovative, music-based audio metric, which:
- correlates well to perceived sound quality
- is understandable to people without technical background; more ►
- uses clear and simple measurement method with open source measurement software; more ►
- measurement procedure is mature enough thanks to two years of beta testing with 30+ players; more ►
These audio measurements are shown in df-slides. One player - one slide. The most meaningful value on df-slide is histogram median, which is assumed to correlate well to perceived sound quality (the research is still in progress). The less the value, the higher playback fidelity. The opening map summerises such medians for all tested players.
How To Read Df-slides
The new audio metric has only one measurable parameter - the Difference Level (Df, dB) which measures degradation of an input signal waveform in a device under test. Input (reference) signals can be of any kind - sine, white noise, music, voice, etc. Df-slide shows such Df measurements with some basic technical signals and real-life audio material.
A set of resulting Df values is in fact an objective representation of so called sound signature or, to be more correct, artifact signature of a device.
How audio quality is measured
During the measurement procedure a portable player plays various music material and technical signals, while high resolution recorder records signal at the player's headphone jack. Afterwards, special algorithm compares initial and output waveforms and computes Difference Level(s) [Df, dB] for the latter.
Early research shows that in most cases such levels of degradation, computed with substantial amount of sound material, correspond well to perceived sound quality estimations.
The test sequence at the moment consists of 10 technical signals (sine, square, white noise, ...) and 35 full tracks of various genres, 2 hours in total (SE test set of music material "Variety").