Audio Capture

The perry/system module provides real-time audio capture from the device microphone, with A-weighted dB(A) level metering and waveform sampling — everything needed to build a sound meter, audio visualizer, or voice-level indicator.

import { audioStart, audioStop, audioGetLevel, audioGetPeak, audioGetWaveformSamples } from "perry/system";

Quick Example

import { App, Text, VStack, State, Canvas } from "perry/ui";
import { audioStart, audioStop, audioGetLevel, audioGetPeak, audioGetWaveformSamples } from "perry/system";

audioStart();

const db = State(0);

// Poll the level every 100ms
setInterval(() => {
  db.set(audioGetLevel());
}, 100);

App({
  title: "Sound Meter",
  width: 400,
  height: 300,
  body: VStack(16, [
    Text(`${db.value} dB`),
  ]),
});

API Reference

audioStart()

Start capturing audio from the device microphone.

const ok = audioStart(); // 1 = success, 0 = failure

On platforms that require permission (iOS, Android, Web), the system permission dialog is shown automatically. Returns 1 on success, 0 on failure (e.g., permission denied, no microphone).

audioStop()

Stop audio capture and release the microphone.

audioStop();

audioGetLevel()

Get the current A-weighted sound level in dB(A).

const db = audioGetLevel(); // e.g. 45.2

Returns a smoothed dB(A) value (EMA with 125ms time constant). Typical ranges:

• ~30 dB — quiet room
• ~50 dB — normal conversation
• ~70 dB — busy street
• ~90 dB — loud music
• ~110+ dB — dangerously loud

audioGetPeak()

Get the current peak sample amplitude.

const peak = audioGetPeak(); // 0.0 to 1.0

Returns a normalized amplitude value (0.0 = silence, 1.0 = clipping). Useful for simple level indicators without dB conversion.

audioGetWaveformSamples(count)

Get recent dB samples for waveform visualization.

const samples = audioGetWaveformSamples(64); // array of up to 64 dB values

Returns an array of recent dB(A) readings from a 256-sample ring buffer. Pass the number of samples you want (max 256). Useful for drawing waveform displays or level history charts.

getDeviceModel()

Get the device model identifier.

import { getDeviceModel } from "perry/system";

const model = getDeviceModel(); // e.g. "MacBookPro18,3", "iPhone15,2"

Platform Implementations

All platforms capture at 48kHz mono and apply the same A-weighting filter (IEC 61672 standard, 3 cascaded biquad sections).

Next Steps

• Camera — Live camera preview (iOS)
• Overview — All system APIs