Purpose
Most headphones depend to some degree on an effective seal to the head or ear by the earpads or, in the case of insert headphones, the flexible ear tips. If this seal is compromised – as it can easily be with over-ear headphones where the earpads seal against hair and/or the user may be wearing spectacles – headphone bass response will often suffer. This test determines the severity of this effect.
Method
To test for this with circumaural (over-ear) models of headphone, frequency response measurement is repeated with the artificial ear fitted first with the temple arm of a chunky pair of spectacles, and again with the temple arm replaced by a hemp mat which has acoustic resistance similar to that of human hair. The effects of the temple arm and mat are illustrated by overlaying the frequency responses obtained with them in place on the frequency response from the uncorrected responses test, where the earpad rests on a flat, non-porous surface which is much easier to seal to. All three responses are normalised to 0dB at 1kHz. Each capsule is tested separately, the measurement procedure being the same as that used to obtain the headphone’s uncorrected frequency responses.
Measurement parameters (wired headphones)
Test signal: pink-spectrum periodic noise
Sampling frequency: 96kHz
Bit-depth: 16 bits
FFT length: 32,768pt
Frequency resolution (measurement): 2.93Hz
Frequency resolution (graph): 1/100th octave
Reseats on the artificial ear: 10 per condition
Measurement averages: 10 per reseat
IR windowing: adaptive
Measurement parameters (Bluetooth headphones)
Test signal: pink-spectrum periodic noise
Sampling frequency: 48kHz
Bit-depth: 16 bits
FFT length: 16,384pt
Frequency resolution (measurement): 2.93Hz
Frequency resolution (graph): 1/100th octave
Reseats on the artificial ear: 10 per condition
Measurement averages: 10 per reseat
IR windowing: adaptive