Binaural recordings are made by placing microphones directly in one's ear, capturing the sound that reaches the pinnae. By playing back the recording through headphones, one ensures that each of the listener's ears get the exact same signal as originally captured. The result is immersive and truly surprising, but only works with headphones.

Our test signal consists of a binaural recording of someone knocking on wooden doors. When comparing headphones, judge how realistic the recording sounds: do you feel as if the doors are right next to you? Does it sound like real wooden doors?

Headphones that are properly wired will route the left channel to the left earpiece, and the right channel to the right (this makes sense). More important, relative polarity between drivers must be preserved: when presented with the same input signal, both drivers should move in the same direction, not opposite of each other.

Better headphones have tighter tolerances in the variation of their drivers' frequency responses. To reproduce a faithful stereo image, the left and the right drivers must respond equally to every frequency in the audible spectrum. When this condition is fulfilled, the drivers are said to be "matched."

Our driver matching test sweeps all these frequencies (up to 10 kHz) and sends exactly the same levels to both earpieces. Play the test tone at a moderate level and listen: the sweeping tone should keep a perfect central position across all frequencies, playing right in the middle of your head, without any deviation.

A panning that departs from its central position for a particular frequency will highlight poorly matched drivers... or mismatched ears.

To ensure that your headphone’s drivers cause the problem, not your ears, perform the test again, with the earpieces swapped: the left channel now feeding your right ear and vice versa. The panning should now deviate in the opposite direction.

Poorly built or extensively worn headphones may start to rattle whenever loud or deep bass content is played. The next file scans bass frequencies and will literally shake your drivers when turning the level up. Adjust the volume in your headphone so that the test is made at a high level: the sweeping tone should remain pure and clear at all frequencies, without any parasitic buzz or rattle appearing in one earpiece or the other.

Dynamic range represents the ratio between the loudest signal you can hear and the quietest. Dynamic range is not part of any headphone specification, but will help you when benchmarking the isolation offered by your headphone in a noisy environment.

The file starts by playing noise at a full scale level. Adjust the level in your headphone so that this noise plays loudly, without being uncomfortably loud. Right after the noise, a voice is played back at a specified level, expressed in dBFS (decibels below full scale). Noise references and voiceovers alternate with each other, with the voice being played at decreasing levels. Play the file until you can't hear the voiceover anymore. The dynamic range that has been reached is given by the level the voice message was playing at when it was still (barely) audible.

The higher the dynamic range reached, the better the isolation offered by your headphones.

In general, "closed" headphones and "in-ear" earphones provide more isolation than the "open" type of headsets.

Ideally, you want your headphones to reproduce all frequencies consistently between the lower and upper limits, without a dip or peak in a particular frequency range. Absolute flatness is not exactly what you are looking for, though. Your hearing may not be perfect, and if you think about it, the best headphones are those that compensate for your particular hearing curve. It doesn't matter if your headphones are not flat, as long as they sound flat through your ears.

Frequency responses are measured using sine sweeps and special test equipment. With a prominent sensitivity bump around 1–3 kHz, humans are not good at judging flatness: frequencies in the upper medium range will always sound louder than what they are because of the increased hearing sensitivity. Our test tone is not a regular sweep. It embeds an inverted hearing sensitivity curve that turns it perceptually flat. Our compensation only works at hearing threshold levels: turn your computer level down so that the test tone plays as quietly as possible.

If the sweep keeps playing at your hearing thresholds, your headphones are matched to your ears. If your hearing is perfect, this also means that the headphones have a flat frequency response. If your hearing is imperfect, this then means that your headphones are simply matched to your ears. If the test tone sometimes disappears, or gets too loud, you know you have a problem, either with your hearing or your headphones.

This test is of particular importance for earbuds. Depending on how deep you insert them into your ear canal, their frequency response will change drastically. Use this test to find which insertion depth gives you the flattest frequency response.

The second file tests your headphones’ treble extension. To measure your headphones’ highest frequency, play back the second file until you start hearing the underlying (high pitched) sweep tone as it descends. Good headphones will reproduce frequencies up to 20 kHz, the upper limit of human hearing range.

Beware though: 1/ this limit decreases as we age. If all of your headphones suddenly exhibit the same upper frequency limit, and this frequency is lower than what is specified by the manufacturer, suspect your hearing, not the quality of your headphones. 2/ If you hear strange ups and downs or anything else that does not sound like a continuously descending sweep, suspect your sound card and aliasing.

The first file tests your headphones' bass extension. Play back the file until you start hearing the underlying sweeping tone as it rises. The voiceover tells you the frequency you have reached: this number represents the lowest boundary of your headphones or earbuds frequency extension. Good headphones will go as low as 20 Hz, the lowest limit of our hearing.