Earasers response curves

Your ear canal is a tuned tube. It boosts sound around 2.5–3.5 kHz before it reaches the eardrum. An earplug changes what arrives there. The level at the eardrum with a plug in follows REAG = REUR + REIG.

Your ear is a resonating chamber

The ear canal is a small tube closed by the eardrum. Like blowing across a bottle, it rings at its own frequency. In an adult it boosts sound near 3 kHz by up to 18 dB. Audiologists call this boost REUR.

The earplug attenuates

Putting a plug in reduces the sound. That reduction is the plug's attenuation, measured as REIG. It is not the same at every frequency: the plug also stops the ear canal from ringing, so the 2–4 kHz region drops the most.

The new shape at your eardrum

Add the two together. Ear canal boost plus plug attenuation gives the resulting shape of your ear's response at the eardrum with the plug in, called REAG. Filtered plugs keep that shape close to the open ear's, so music sounds quieter but still clear.

Venue · sets the concert level (dBA)

Listener

Or a fixed test level · compares styles fairly

Sound

Earplug

Show all filters on the ear chart

Reading the ratings. SNR is the European rating (EN 352-2, tested under ISO 4869). NRR is the US rating (ANSI), calculated differently and usually a few dB lower for the same plug. The filter names (−19, −26, −31 and −36 dB) describe peak reduction. The −19 dB name comes from Virginia Tech testing and the −31 dB name from Michael & Associates, both from Earasers' US launch. The −26 dB name comes from Earasers' first CE-tested earplug in Europe, the SNR 20. The −36 dB filter is our sleep and comfort plug; its name is an estimate, since a sleep plug did not need US testing. The curves below are real-ear measurements at the eardrum, so they won't match any single rating number exactly.

Your noise exposure

Safe daily time · NIOSH85 dBA for 8 h, halved every 3 dB · a guideline, not a guarantee

Loudest band at eardrum

Discomfort zone

Match loudness to compare tone Volume

Plays a short generated groove in the music style you picked, shaped by the selected filter's insertion response. Headphones work best. Keep the volume comfortable: your speakers can't reach concert levels, so this shows how the sound changes, not how loud a show is.

Spectrum at the eardrum

What the ear and the plug do

Measured against the sound at the ear entrance. Above zero, the ear canal boosts the sound. Below zero, the plug attenuates it. Notice how the attenuation changes across frequency.

Terms

REUR · real-ear unaided response: The open ear canal's resonance: how much louder each frequency is at the eardrum than at the ear entrance.
REIG · real-ear insertion gain = attenuation: How much the plug changes the sound at the eardrum compared with the open ear. For an earplug it is negative, so REIG is the plug's attenuation: −20 dB means 20 dB quieter at that frequency.
REAG · real-ear aided gain: The resulting shape of the ear canal response at the eardrum with the plug in: the ear's boost plus the plug's attenuation. REUR + REIG.

How the numbers are made

Adult male REUR and the four filter curves are read from the Earasers attenuation chart (95 dB input). Other ages shift the resonance peak by ear canal length: about 7.2 kHz at birth, falling to the adult 2.7 kHz by 12–24 months (Kruger 1987). Children 3–13 are close to adults, with wide individual variation (Bentler 1989). Peak height is kept at the adult value because published amplitudes by age were not available.

With a plug in, the eardrum level follows the filter's adult REAG, plus an estimated lift for the smaller air space behind the plug in younger ears (up to about 5 dB at high frequencies for newborns). REIG is then REAG minus that listener's REUR, so a plug takes away whichever resonance that ear has.

Music spectra are illustrative long-term averages, scaled so their A-weighted sum equals the concert level. Venue levels are rough averages, from about 82 dBA in a coffeehouse to 110 dBA in the front row; real shows vary widely. Motorcycle cruising is set to 100 dBA under a helmet at highway speed; wind noise rises with speed and can pass 110 dBA. The single-piston cockpit is set to 92 dBA in cruise without a headset. Both are dominated by low-frequency noise, where earplugs attenuate least, and some engine and wind vibration reaches the inner ear through the skull, which no earplug blocks. "Flat test" puts every band at the chosen level, like the original chart.

The foam reference is a typical deep-inserted foam earplug, using approximate published lab attenuation. Foam blocks the ear canal and cuts high frequencies much more than low ones, so the resulting shape at the eardrum is dull and muffled. Real-world foam fit is often shallower, with less attenuation.

The listening demo is synthesized in your browser. It applies the selected filter's insertion response (REIG) to the sound, so you hear the change a plug makes relative to your own open ear.

Limits

The discomfort zone is an approximation of the 100-phon equal-loudness (Fletcher–Munson) contour, used as a teaching guide. Exposure is the A-weighted level at the ear entrance minus the plug's attenuation. Individual ears and fit vary by several dB.