# Audio Oscilloscope

> View sound card signals as a waveform, spectrum or Lissajous figure in your browser. Triggers, frequency, phase and a tone generator. Nothing uploaded.

- URL: https://bytescope.dev/en/audio-oscilloscope/
- Locale: en · Also: [ja](https://bytescope.dev/ja/audio-oscilloscope.md) · [zh-Hant](https://bytescope.dev/zh-Hant/audio-oscilloscope.md)
- Runs: Runs in your browser. The input is read here and never uploaded.
- Requires: Needs AudioWorklet and getUserMedia, both in a secure context. Chrome and Edge are the targets; Firefox and Safari are untested. Your browser may keep the operating system audio enhancements on, which this page cannot turn off, so check the readout.
- Updated: 2026-09-08

## What it does

### What you can see

This page turns your sound card into a two-channel oscilloscope for audio-level signals. In YT mode you see the waveform over time, with both channels drawn on the same grid. In XY mode one channel is plotted against the other, which draws a Lissajous figure. In FFT mode you see the spectrum on a logarithmic frequency axis. A trigger keeps a repeating waveform still, and the measurements panel reads frequency, period, peak-to-peak, RMS, duty cycle and the phase between the two channels.

### How the readings are made

Everything is computed in your browser from the samples the sound card delivers. Amplitudes are fractions of full scale, where 1.0 is the largest value the converter can produce, until you calibrate the input against a known voltage; then they show volts. Frequency comes from averaged zero crossings, so the screen must hold at least two full periods. The tone generator plays test tones through your output device, which helps when you check cables, channels and a loop from output to input.

### What it cannot do

It is not a replacement for a real oscilloscope, and it is not made for mains, power electronics or fast digital signals. The input is AC-coupled, the bandwidth stops near 20 kHz, and your operating system may keep audio enhancements switched on. The limits section on the page lists each one.

## Limits

Does not read DC, does not see anything above about 20 kHz, and does not show timing of digital signals or PWM edges. It cannot measure mains or high voltage and is not a replacement for a real oscilloscope. The sound card input is AC-coupled, so square-wave tops droop and the amplitude is uncalibrated until you calibrate it.

## FAQ

### Can I connect mains voltage or a transformer to it?

No. Never connect mains (110 V or 220 V), a transformer secondary or any high-voltage circuit to a sound card input. It can damage the computer and can kill you. A sound card is built for line-level and microphone signals only, and a voltage divider does not make mains safe to measure here.

### Why does the top of my square wave slope down?

The input is AC-coupled, which blocks the DC part of the signal. The flat top of a square wave then slowly droops toward the average level. This comes from the hardware, and no software setting removes it.

### Why are the numbers not in volts?

By default the amplitude is a fraction of full scale. Feed in a signal of known peak-to-peak voltage, enter that voltage and press Calibrate, and the page then shows volts. The calibration is approximate and is saved only in this browser, for this input device.

### Which browsers work?

Chrome and Edge are the target browsers. The page needs AudioWorklet, getUserMedia and a secure https address. Firefox and Safari have not been tested for this page, so check the readings against a signal you know before you trust them.

### Is my audio uploaded anywhere?

No. The input is read in your browser only. Nothing is sent to a server, and the CSV and PNG files you export are saved on your own device.

## Related tools

- [Mic Test](https://bytescope.dev/en/mic-test.md) — Check microphone input levels and processing
- [Speaker Test](https://bytescope.dev/en/speaker-test.md) — Play left and right test tones on speakers
- [Headphone Test](https://bytescope.dev/en/headphone-test.md) — Check left and right channels on headphones