Guides

The written half of the site: what to check when something is wrong, and what is going on underneath when everything is working.

Fixing a problem

• No sound at all: the checklist The order to check things in when nothing plays, on Windows, macOS, Android and iOS.
• One earbud or speaker not working Isolating a dead side from a blocked nozzle, a broken cable or a balance slider.
• Bluetooth audio problems Delay, one-sided sound, the mono call-quality trap and what actually fixes each.
• Speaker polarity and phase Why one reversed pair of wires makes the bass vanish, and how to hear it.
• Testing audio before a video call A ninety-second routine that catches the faults that waste the first five minutes of a meeting.

Understanding sound

• Audio frequency chart What lives where between 20 Hz and 20 kHz, from a kick drum to a cymbal.
• Hearing range by age Why the top of the range narrows, roughly how fast, and what it does and does not mean.
• Sine, square, sawtooth and triangle What the four waveforms sound like, what is inside them, and when to use each.
• 432 Hz against 440 Hz Where each number came from, what the claims are, and what the evidence shows.
• The mosquito tone The 17 kHz tone most adults cannot hear, and the devices built around it.
• Stereo against mono What the second channel buys you, and how a device ends up stuck in mono.
• How loud is too loud Decibels, exposure time, and the reason volume limits are about hours as much as level.

Getting the most out of your gear

• Subwoofer test tones Which frequencies to use for placement, crossover and level, and in what order.
• Testing a car audio system Fader, balance, door rattles and the tones that find each of them.
• Headphone burn-in What changes, what does not, and how to tell the difference from getting used to a sound.

Tools

• Sound testThe full five-step check: left, right, stereo, bass and top end.
• Tone generatorAny frequency from 1 Hz to 22 kHz, four waveforms, either channel, downloadable as a WAV.
• Speaker testFor desk and laptop speakers: channel order, imaging and how low the box really goes.
• Headphone testLeft and right, centre image and top end, with the checks that only matter on headphones.
• Left / right testThirty seconds to find out whether a channel is dead or just wired backwards.
• Bass testSweep from 20 Hz up and find the point where your speakers start producing anything.
• Hearing range testHow far up the spectrum you and your headphones still get. A fun test, not a medical one.
• DTMF tonesPlay and read the two-tone pairs behind every phone keypad digit.