Audio oscilloscope
Press Start, allow the microphone and the wave appears. Whistle or hum and you will see a regular pattern; speech and noise look irregular. The signal is drawn live in your browser and never recorded or sent.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Press Start scope and allow the microphone.
- Pick a Time window of 5, 10, 20 or 50 ms; a shorter window zooms in on the wave.
- Raise Vertical gain (×1, ×2, ×5, ×10) for quiet sounds.
- Freeze holds the picture so you can look at it; Resume continues.
How it works
The browser’s analyser provides 4096 recent samples, each between −1 and +1. The page finds the first rising zero crossing in the first half of that buffer, draws the number of samples that fit the chosen window (the sample rate times the window length) and scales the amplitude by the gain. The faint grid has 10 divisions across and 4 down.
Worked example
At a 48 kHz sample rate a 20 ms window is 0.020 × 48 000 = 960 samples across the screen. A 440 Hz tone has a period of 1 / 440 = 2.27 ms, so about 8.8 waves are shown.
Tips
- Use a short window for high notes and a long one for voice.
- A pure tone from the tone generator on another device gives a clean sine for comparison.
Frequently asked questions
Is the sound recorded or uploaded?
No. The page reads the current samples from the browser's audio analyser and draws them. Nothing is stored or sent, and Stop turns the microphone off.
What is the trigger?
Every frame the drawing starts at the first point where the wave rises through zero. That makes a steady tone hold still instead of scrolling. If the signal never crosses zero, drawing starts at the first sample.
How do I read the frequency from the screen?
Count how many full waves fit in the time window. If 4 waves fit in 20 ms, one wave takes 5 ms, so the frequency is 1 / 0.005 s = 200 Hz. For an automatic reading, use the instrument tuner or the spectrum analyzer.
Why does the wave look clipped flat?
When the signal is above full scale, or the gain is raised, the trace is cut at the top and bottom of the screen. Lower the gain or move away from the microphone.