ePRB Subjective Speaker Test

A test sequence that enables you to make perceptual Rub & Buzz measurements and compare them to your subjective opinion

Introduction

This sequence demonstrates how SC20’s new enhanced Perceptual Rub & Buzz algorithm compares to normalized Rub & Buzz and subjective listening. Running this sequence on a batch of good and bad buzzing loudspeakers should help identify by measurement, audibly defective units and where to set production limits.

Starting the sequence, the user is asked at what test level to play a stepped sine sweep (Stweep™) in 1/12^th octaves, from 20 kHz to 50 Hz. The user is encouraged to try different test levels and change sweep parameters to find the optimum settings to catch buzzing loudspeakers. The loudspeaker is measured via two channels of the audio interface. A calibrated reference microphone is connected to one of the channels and an impedance reference built into the SC Amp or AmpConnect is connected to the other. A HarmonicTrak™ Analysis step analyzes the recorded waveform from the reference microphone, and displays both the enhanced Perceptual Rub & Buzz and normalized Rub & Buzz graphs.

The user is asked if they want to save the measurements and if yes, are prompted to subjectively rate the audible Rub & Buzz on a scale from 1 to 5 (1 = no audible Rub & Buzz, 2 = just audible, and 5 = very audible) and provide a description of the sound quality in the following Prompt for Comment step. Then the recorded waveforms are saved and data plus rating exported to Excel for documentation. The spreadsheet “Example Listening Results.xlsx” is provided as an example of listening test sequence results.

We would appreciate if customers would share their data with us so we can confirm the subjective validity of their measurements and use it to further refine our algorithm if necessary. It will also be quite useful in helping customers define Rub & Buzz limits on the production line. Please zip your “Measurements” folder contained within the same folder as our “ePRB Subjective Speaker Test.sqc” to support@listeninc.com.

Required Software

• SoundCheck 20 or later

Required Hardware

• Reference Microphone – Listen SCM-4 or similar
• Audio Interface – Listen AudioConnect, AmpConnect or similar (note: AudioConnect provides bias voltage for Listen’s SCM microphones. If you use a different microphone or interface, you will likely need to add a microphone power supply such as the Listen SoundConnect to your hardware setup.)
• Power Amplifier – Listen SC Amp or similar

Setup Diagram

Hardware Setup and Calibration

1. Calibrate the amplifier as instructed in the SoundCheck manual.
2. Calibrate the reference microphone as instructed in the SoundCheck manual.
3. Connect output 1 of your audio interface to the input of the amplifier.
4. Connect the output of the amplifier to your loudspeaker.
5. Position your reference microphone at the desired test distance from the loudspeaker and connect it to the microphone power supply.
6. Connect the mic to input 1 of your audio interface
7. Connect the impedance sense out from the amplifier to input 2.

You are ready to start the sequence.

Get Sequence

Download Sequence (zip file)
Download Sequence documentation (PDF)