ByteScope

Audio Oscilloscope

Turn your sound card into a two-channel oscilloscope for audio-level signals, with triggering, FFT, measurements and a built-in tone generator. Everything runs in your browser.

Runs in your browser. The input is read here and never uploaded.

Safety: small signals only

Never connect mains (110 V or 220 V), a transformer secondary or any high-voltage circuit to a sound card input. It can damage your computer and can kill you. Use this page only for line-level signals (about 1 V peak-to-peak, at most about 2 Vpp) and microphone-level signals. Professional equipment (+4 dBu) can reach about 3.5 Vpp, so attenuate it before you connect it. Reduce anything bigger with a voltage divider first.

Ground loops cause hum and can damage equipment. Connect the grounds of the two devices before you connect the signal.

VinR1R2To input

Voltage divider for larger signals

Vout = Vin × R2 ÷ (R1 + R2). For example, R1 = 9.1 kΩ and R2 = 1 kΩ (standard E24 values) divide the signal by about 10.1. Use resistors rated for the power, and measure the output with a multimeter before you connect it to the input.

Input

Checking your browser…

Tone generator

The generator plays through your output device. Turn the volume down first, and keep headphone volume low.

Left
Right

Phase is set when a tone starts, so changing a value while playing restarts it. The sweep runs once for 5 seconds and ignores frequency and phase.

Limits

  • Bandwidth is about 20 kHz. Fast PWM edges and digital timing are not visible.
  • The input is AC-coupled, so DC is not measured and the flat top of a square wave slowly droops.
  • Amplitude is uncalibrated by default. A calibration is approximate.
  • Audio enhancements such as Windows enhancements or macOS Voice Isolation may stay on, and the browser cannot switch them off. On Windows, check Sound settings, then the Properties of your input device, under Enhancements or Advanced. On macOS, check Mic Mode in Control Center.
  • The combined headset jack on most laptops is a mono microphone input, so it shows one channel.

About this tool

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.

Frequently asked questions

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