Every tool on this site is checked in two ways: automated tests that run on every change, and hands-on checks with real equipment before the tool goes live. This page explains both, and what a browser can't measure.
Automated checks on every change
- Unit tests check the math behind each tool with known inputs. For example, the volume code must never start a sound louder than 30%, and a synthetic 440 Hz tone must read as A4.
- Browser tests open every page in Chromium at phone and desktop sizes, run the main steps with a simulated microphone, and fail on any error in the browser console.
- Accessibility scans with axe must find no serious problems, and every control must work with a keyboard alone.
- Page checks confirm titles, descriptions, links and structured data before anything is published.
Hands-on checks before a tool goes live
A simulated device can't tell whether the left channel really plays on the left. So before a tool goes live, I use it myself on real hardware and a phone:
- Browsers: Chrome and Edge on Windows, Safari on macOS and iPhone, Chrome on Android, plus Firefox for tools that rely on newer browser features.
- Equipment: AirPods Pro 2 and a Jabra Evolve 55 headset for the headphone and mic tests, a JBL Flip 5 and laptop speakers for the speaker tests, the built-in mics on my laptops and phones, and my guitar for the tuners. The phones and computers are an iPhone 15 Pro, a OnePlus 10, a Lenovo ThinkPad and a MacBook Air.
- Not in the kit yet: a surround system and a separate subwoofer. For those two tests I lean on the automated checks above and on reports from readers who own one.
How accuracy is checked
| Tool type | Reference | Passes when |
|---|---|---|
| Instrument tuners | A 440 Hz tone from a second device, then tones 10 cents sharp and flat | It reads A4 and the detuning within ±2 cents |
| Tone generator | A spectrum analyzer app on a second device | The peak sits at the set frequency, within ±1 Hz below 1 kHz |
| Tap tempo and BPM finder | Metronome tracks and songs with a known tempo | Within ±1 BPM, or exactly half or double, which the tool lets you correct |
| Mic test level meter | The input meter in Windows sound settings | Both meters move together, and clipping shows when the system meter maxes out |
| Left/right and surround tests | The speaker test in Windows sound settings | The same speaker plays for the same channel |
| Recorders and audio cutters | Playing the saved file in VLC and on a phone | It plays, has the right length and format, and has no clicks at the cut points |
What a browser can't measure
Some things need dedicated equipment. The tools say so instead of guessing:
- Loudness in dB SPL. A browser doesn't know your volume setting or how sensitive your speakers are. Level meters show dBFS, relative to the most the device can handle.
- Frequency response. Measuring how evenly a speaker or headphone plays every pitch needs a calibrated measurement microphone.
- Hearing. These tools check equipment, not people. If you're worried about your hearing, talk to a qualified professional.
How often tools are re-checked
Every live tool gets a quick check each month on a computer and a phone. Each page is reviewed in full at least every 6 months, and right away if a browser update breaks something. The date at the top of each page shows its last real update.
Found a problem?
Email contact@audiotesttools.com with the page address, your browser and device, and what happened. Every tool page also has a "Report a problem" link at the bottom.