Speaker cleaner, bass test and hearing range: what the test tones do

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Three tones turn up again and again in search: the sound that gets water out of a phone speaker, the sweep that tests how low a speaker goes, and the sweep that supposedly tests your hearing. They are all simple to generate. What they actually tell you, and how to use them without damage, is less obvious.

Speaker cleaner: a 165 Hz tone

When a phone gets splashed, water sits in the speaker grille and the sound comes out muffled. Apple Watch has had a Water Eject feature for years. It plays a low tone, around 165 Hz, at full volume for a few seconds. The cone moves a long way on each cycle and physically pushes the droplets out.

Most Android phones do not have a built-in version, so people play the tone themselves.

How to do it:

Turn the phone's volume all the way up. The built-in speaker cannot get loud enough to hurt you.
Hold the phone with the speaker grille facing down so the water has somewhere to go.
Play the tone for 10 to 30 seconds. You may see droplets appear on the grille. Wipe them off.
Repeat two or three times, then leave the phone to dry.

What it will and will not do:

It helps with a few drops after rain, a sink or a shower.
It does not fix a phone that has been submerged. Water inside the case is a different problem, and playing tones does not reach it.
It does nothing for a speaker clogged with lint or pocket dust. That needs a soft brush and patience.
Do not plug in a charger until the phone is dry. Most phones warn you about liquid in the port, and that warning is worth obeying.

Bass test: a sweep from 200 Hz down to 20 Hz

A sweep is a tone that glides from one frequency to another. Running it slowly downwards is the easiest way to find out where a speaker, a pair of headphones or a subwoofer gives up.

Start at 200 Hz and take about 30 seconds to reach 20 Hz. Listen for three things:

Where it fades. At some point the tone simply gets quieter and disappears. That is the low limit of the driver. A phone speaker fades almost immediately, often above 300 Hz. Earbuds usually carry on to around 40 or 50 Hz. Good over-ear headphones and a subwoofer reach 20 Hz.
Rattles and buzzes. A clean sweep should sound like one smooth tone. A buzz at one particular frequency means something is loose and resonating: a grille, a cabinet panel, a picture frame on the shelf behind the speaker.
Chuffing. On a ported subwoofer, a puffing noise at the lowest frequencies is air rushing through the port. It means you are past what the box can do cleanly.

Keep the volume moderate. Small drivers can be damaged by very low frequencies at high level, because the cone travels further than it was built for and nothing sounds loud to warn you.

Hearing range: a sweep from 8 kHz to 20 kHz

The upper limit of human hearing is about 20 kHz in childhood and drops with age. Everyone has seen the online test: a rising tone, and the moment it goes silent is "your age".

Run a sweep from 8 kHz up to 20 kHz over 30 seconds, linear so each second is the same step. Note where it vanishes. Rough averages:

Age	Typical upper limit
Teens	17 to 20 kHz
Twenties	16 to 17 kHz
Thirties	15 to 16 kHz
Forties	14 to 15 kHz
Fifties	12 to 14 kHz
Sixties and up	12 kHz or below

Now the caveats, which matter more than the table:

You are testing the device too. Phone speakers and many cheap earphones roll off hard above 15 or 16 kHz. If the sweep goes quiet at 15 kHz, you do not know whether it was your ears or your earbuds.
Volume changes the answer. Turn it up and the limit moves higher, because faint high frequencies become audible. That is why this is not a measurement.
It says nothing about the hearing that matters. Hearing loss that affects daily life sits in the speech range, roughly 500 Hz to 4 kHz. You can hear 18 kHz and still struggle to follow a conversation in a restaurant.
Do not chase the silence. When the tone fades, the instinct is to turn it up. Do not. A pure tone at high level concentrates all its energy on one spot in the inner ear, and the cells there take the whole load.

If you are worried about your hearing, an audiologist with a calibrated booth gives you a real answer in half an hour.

Volume, once more

Test tones are more dangerous than music at the same perceived loudness. A pure tone has no peaks to startle you and no spread across frequencies to share the load. Before pressing play through headphones: set the level with them off your ears, then put them on. Keep sessions short. Stop at any pressure, fullness or ringing.

Where a tone generator fits

All three of these are presets in Tone Generator: Speaker cleaner is a 165 Hz tone, Bass test is a logarithmic sweep from 200 to 20 Hz over 30 seconds, Hearing range is a linear sweep from 8 to 20 kHz over 30 seconds. The Sweep mode lets you build your own, from 5 to 120 seconds, with as many legs as you like, and a live scope shows the wave as it plays. The app shows a hearing safety notice before first use and keeps it one tap away afterwards.

It is not a hearing test and does not pretend to be one. It is a signal generator with the three most asked-for signals already set up.

Questions & answers

Does the speaker cleaner sound actually work?expand_more

For a few drops after a splash, usually yes. A low tone at full volume moves the speaker cone a long way on every cycle and shakes water out through the grille. It will not rescue a phone that has been under water, and it does nothing for a speaker that is muffled by lint rather than water.

What frequency cleans a speaker?expand_more

Around 165 Hz, the same tone the Water Eject feature on Apple Watch plays. Phone speakers reproduce it loudly enough to move water while still being low enough for a large cone movement. Anything from about 150 to 200 Hz does much the same.

How do I test how low my speaker goes?expand_more

Play a slow sweep downwards from 200 Hz to 20 Hz at moderate volume. The point where the tone fades to nothing, or turns into a rattle, is the bottom of that speaker. A phone speaker gives up almost at once. A good pair of headphones carries on to 20 Hz.

Can I test my hearing with a tone generator?expand_more

You can find out roughly where high frequencies stop being audible on that device at that volume. It is a party trick, not a hearing test. Cheap earphones and phone speakers roll off before your ears do, and the result says nothing about the speech frequencies that matter for hearing loss. A real hearing test is done by an audiologist with calibrated equipment.

What is the highest frequency a human can hear?expand_more

Children often hear up to 20 kHz. The limit falls steadily with age, roughly to 16 or 17 kHz in the twenties, around 15 kHz by the forties and 12 kHz or lower past sixty. Loud music and noisy work bring the limit down sooner.

Is it safe to play test tones at full volume?expand_more

Only the speaker cleaner, and only through the phone's own speaker, which cannot get loud enough to hurt. Never play a sweep at full volume through headphones. Where a sweep goes quiet, the temptation is to turn it up, and that is exactly how people hurt their ears or their drivers.