Vekhyat Jain
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IEM listening test

A listening test that estimates an in-ear monitor’s frequency response from where you can just hear each band.

Status
Working experiment
My role
Solo project
Runs
Offline, in a browser
What it isn’t
A medical test or a calibrated measurement

The question

Measuring an in-ear monitor properly takes an ear simulator, a calibrated microphone, and a rig most people don’t own. The question behind this project was simple: how much of that picture can you get with only your own ears and a careful method?

How it works

  1. Set up. Name the IEM, pick an ear, and choose 10 octave bands for a quick run or 28 third-octave bands for a full one. Each tone is a pulsed warble, because a wavering sound is easier to notice at the edge of hearing.
  2. Check the level. Confirm a soft 1 kHz pulse is audible, then leave the system volume alone for the rest of the test. Every result after this depends on that volume staying put.
  3. Find each threshold. For every band you answer heard or not heard. The level drops 10 dB after a yes and rises 5 dB after a no, the Hughson–Westlake method audiologists use. The threshold is the average of four reversals.
  4. Read the results. A table and a chart with two curves, exportable as CSV or JSON.

Two curves, and the ear in between

Raw sensitivity is how much softer or louder each band was at threshold compared with 1 kHz. It shows what you actually heard, so it includes your ear. Bass looks weak partly because human hearing is much less sensitive there, not only because the IEM rolls off.

The IEM estimate subtracts an average hearing curve, the ISO 226:2003 threshold contour, so a perfectly flat IEM should land near 0 dB across the bands. That curve is below: the quietest sound an average young listener can hear at each frequency.

Average hearing threshold by frequency ISO 226:2003 0-phon threshold from 20 Hz to 16 kHz. It is about 78 dB SPL at 20 Hz, falls to about 2 dB at 1 kHz, reaches its lowest near minus 6 dB around 3 kHz, then rises to 24 dB at 16 kHz. 0 20 40 60 80 20 100 1k 10k Frequency (Hz) Threshold (dB SPL) 1 kHz reference

Values from the ISO 226:2003 0-phon table the tool uses. Lower means more sensitive. The dip around 3 kHz is where the ear canal’s own resonance helps.

What it can’t tell you

  • Both curves are relative. Neither is an absolute level in dB SPL. They only show differences between bands.
  • The estimate corrects for an average ear, not yours. Your own hearing, how deep the tips sit, and the seal all still shape the result.
  • It is not a hearing test and not a coupler measurement.

Start quiet. The tool limits its own output, but your system, DAC, or amp can still be loud, and IEMs seal the ear canal, so all of that sound goes straight in.

Where it stands

It works as a local, offline page. Comparing two IEMs with it is the fun part: same ears, different IEMs, and you can see the difference on the chart.

IEM listening test on GitHub