Headphones Test Sequence
The purpose of this sequence is to test a stereo headphone
The purpose of this sequence is to test a stereo headphone. Both left and right earphones are measured simultaneously using a standard 1/12th Octave stepped-sine sweep from 20 Hz to 20 kHz.
The analysis is then performed using Listen’s HarmonicTrak™ algorithm that measures harmonic distortion and fundamental frequency response simultaneously. Then the diffuse-field and free-field corrected Fundamentals are calculated. The diffuse-field correction curve compensates for the overall frequency response from the diffuse-field (sound in every direction) to the eardrum and includes the effects of the head, torso, pinna, ear-canal and ear simulator. The free-field correction curve compensates for the overall frequency response from the free-field (sound at 0 degree incidence to the nose of the Head and Torso Simulator – HATS) to the eardrum.
Further post-processing of the signal compares left and right earphone responses to show the difference curve (magnitude and phase are available). The average sensitivity from 100 to 10 kHz for both left and right earphone is calculated and the total harmonic distortion displayed.
- Audio Interface – Listen AudioConnect or similar (note: AudioConnect includes a self-contained headphone amplifier. If you are using a different interface, it may require the use of an external headphone amplifier)
- 2 Channel Microphone Power Supply – Listen SoundConnect 2 or similar
- Head & Torso Simulator – Bruel & Kjaer 4128C or similar
Hardware Setup and Calibration
Caution: Dynamic headphones typically need very little voltage e.g. 100mV to produce high sound pressure levels; therefore it is best to use a dedicated headphone amplifier. A normal power amplifier can output a voltage level that will damage most headphones if used at full gain.
1. Calibrate the headphone amplifier per the instructions in the SoundCheck user manual.
2. The Head and Torso Simulator (HATS) both left and right ear simulator needs to be calibrated before measuring the headphones. Refer to the HATS manual for further instructions on mounting a microphone calibrator over its artificial ears. In the SoundCheck Microphone calibration editor, select B&K 4231 & UA 1546 ear adaptor for calibrating the B&K 4128 HATS artificial ears (similar in sensitivity to the B&K 4134 pressure mic). Connect the left and right artificial ear outputs to the power supply inputs and the outputs of the power supply to the inputs of the audio interface.
This sequence is available in the Sequences folder of your SoundCheck installation.