ABOUT PAL

 

Sound Quality Evaluation Service

 
 
Why Shall Conduct Sound Quality?
 
  • The purpose of SQ test is to describe what human really percept by using some proper "subjective quantities". Traditional noise emission test, such as ISO7779, only measures the "sound pressure"  by using A, B, C…weighting is hard to satisfy people's demands.
  • Human's hearing can be analogized as a set of complicated filters. Many special phenomena such as masking effect and hearing temporal memory are hard to simulate by conventional equal-bandwidth or equal-percentage filter. SQ test imports the concept of "Psychoacoustics" is a suitable way to assess human’s real sensation.
 
 
Subjective Quantities of Sound Quality Assessment
 
 
  • Loudness :
    It represents the volume that human really sense. Because human have different sensitivities in different frequency range, the result of loudness are usually very different with the result of traditional sound pressure level.

 

  • Prominence Ratio :
    Some devices such as fans or adaptors usually generate annoying noise. Even though its sound level is not very high, people still feel uncomfortable. It is because the noise is constituted by many pure tones. Prominence ratio is used to assess whether these pure tones are prominent or not.

 

  • Modulation :
    When two sounds have similar frequencies and sound level, they may be coupled each other. This phenomenon is so called "modulation". Modulation has two types: amplitude modulation (AM) and frequency modulation (FM). Each of them will let people feel the sound is unstable and not pleasing to the ear.

 

  • Roughness :
    It represents the sound is not very smooth. That is to say, the sound has higher modulation frequency and modulation strength.

 

  • Sharpness :
    The sharpness of sound usually determines whether human like it or not. It is independent of the loudness or sound pressure. It is only decided by the composition of sound. The larger high frequency percentage, the higher the value of sharpness.

 

  • Tonality :
    It represents the stability of sound. If the sound varies seriously in a certain time, it will have larger tonality.

 

 

Facilities
 
  • Chamber
    • Hemi-anechoic room
    • Capacity: 5 x 5 x 3 cube meters
    • Ambient Temperature: 23 ± 2∘C
    • Cut-off Frequency: 100 Hz
    • Background Noise: ≈16.5 dB(A)
  • Hardware
    • Multi-channel frequency analyzer
    • Artificial head
    • Microphone and calibrator
    • Reference sound source
    • RPM meter
    • Standard testing table (ISO 7779)
  • Software
    • Artemis Basic Analysis Software
    • Playback Module
    • Psychoacoustics Module
    • Octave Analysis Module
    • Advanced Psychoacoustics Module
    • Advanced Analysis Module
    • Advanced Filter Module

 

 
Fig.1 Using artificial head to evaluate SQ
 
 
 
 
Fig.2 SQ test example of an NB adaptor. It has a low sound pressure level, but it has very high
prominence ratio and modulation strength. Therefore, although the sound pressure level is very
low, about 20 dB(A), human still feel the noiseis very harsh and fluctuation