CLEAR Perceptual Rub & Buzz Measurement
A test sequence that uses Listen’s Perceptual Rub & Buzz algorithm to measure only those defects audible to the human ear.
NOTE: This feature has been superseded by our new enhanced Perceptual Rub & Buzz algorithm which builds on the methodology of this, but offers better correlation with human hearing and significantly better repeatability and reliability. Please try these two sequences instead:
This sequence demonstrates the Perceptual Rub & Buzz feature in the analysis editor. PRB measures distortion based on human hearing models and masking curves. This results in a distortion measurement that more accurately represents listener perception. The output of this option is a curve that displays distortion in Phons (a unit of loudness) versus frequency. For more information on the Perceptual Rub & Buzz algorithm, read the AES paper written by Steve Temme and Pascal Brunet. It is available for download here.
The sequence begins with a prompt that gives the user the option to load example data from disk or run a new measurement. Example data can be viewed even if the Perceptual Rub & Buzz module is not enabled on the system. If the user chooses to run a new measurement, a stepped sine sweep from 20 kHz to 50 Hz is played, and the frequency response and PRB are measured and displayed. The perceptual distortion curve is measured against a limit of 25 phons across the frequency band.
Initial testing shows that the threshold of audibility for perceptual distortion to be around 20 phons. In practical application, this value should be adjusted depending on the device under test. Varying amounts of distortion may be acceptable in a product depending on its characteristics and target application.
The example data in the sequence shows the perceptual distortion curves for a good, borderline, and bad speaker of the same model. The recorded time waveforms from these tests were also stored and saved as WAV files in the sequence folder. Listen to the WAV files on a high quality pair of headphones to hear the varying levels of distortion in the speakers, and see how this is reflected in the perceptual rub & buzz curves.
- SCM-3 calibrated measurement microphone Part # 4004
- AmpConnect all-in-one hardware interface Part #4042 OR
- SoundConnect Microphone power supply Part # 4020 AND Power amplifier (SCAmp Part # 4060)
- SoundCheck 9.1 or later
- Stepped Sine module Part # 2018
- Limits PN 2000
- Harmonic Distortion PN 2001
- Perceptual Rub & Buzz 2030
Setup & Calibration
- Calibrate the amplifier as instructed in the SoundCheck manual.
- Calibrate the reference microphone as instructed in the SoundCheck manual.
- Connect the channel 1 (or Left) output of your soundcard to the input of the amplifier.
- Connect the output of the amplifier to your loudspeaker.
- Position your reference microphone at the desired test distance from the loudspeaker, and connect it to the microphone power supply.
- Connect the output of the mic supply to the channel 1 (or Left) input of your soundcard.
You are ready to start the sequence.