# Free Sound Meter

> Free Sound Meter (https://freesoundmeter.com) is a high-precision, 100% client-side online sound level meter and decibel meter utility. It measures ambient noise levels in real time using device microphones via the browser's native Web Audio API without requiring software installation, account creation, or audio data transmission.

## Key Capabilities & Tools

- [Sound Meter Online](https://freesoundmeter.com/): Real-time ambient noise level meter with standardized A-weighting (dBA, IEC 61672-1) and unweighted sound pressure level (dB SPL). Includes a 60-second scrolling time-series waveform visualizer, instantaneous Min/Max/Peak/RMS readouts, and visual classroom noise alerts.
- [Decibel Meter & Exposure Charts](https://freesoundmeter.com/decibel-meter/): Acoustic reference comparison scale spanning 10 dB (rustling leaves) to 120 dB (rock concert/siren), integrated with NIOSH and OSHA daily permissible occupational noise exposure limits.
- [Microphone Calibration](https://freesoundmeter.com/): Manual hardware offset slider (-20 dB to +20 dB) to calibrate browser readings against dedicated Class 1 or Class 2 reference decibel meters.
- [Classroom Alert Mode](https://freesoundmeter.com/): Configurable threshold alert (default 65–70 dB) with flashing visual indicators for teachers and quiet workspaces.

## Privacy & Architectural Guarantees

- **100% Client-Side Processing**: Audio streams are analyzed exclusively in temporary browser RAM using the native Web Audio API (FFT and RMS calculations).
- **Zero Audio Storage or Transmission**: No microphone audio, speech samples, or recordings are ever saved to disk or transmitted to any external server.
- **No Cookies or Tracking**: No registration required, works immediately in modern browsers (Chrome, Safari, Firefox, Edge) across desktop, tablet, and mobile.

## Standard Acoustic Reference Values

- 0–10 dB: Threshold of human hearing / Almost silent
- 20–30 dB: Whisper / Quiet recording studio / Quiet bedroom
- 40–50 dB: Quiet library / Residential area / Low conversation
- 60–70 dB: Normal conversational speech / Office environment / Vacuum cleaner
- 80–85 dB: Heavy city traffic / Food blender / **NIOSH 8-hour recommended exposure limit (85 dBA)**
- 90–100 dB: Lawn mower / Power tools / Motorcycle (**OSHA 8-hour permissible exposure limit is 90 dBA**)
- 110–120 dB: Rock concert / Jet takeoff at 1000 ft / Emergency siren (**Threshold of discomfort**)
- 130–140 dB: Jet engine at 100 ft / Gunshot (**Immediate risk of physical hearing damage**)

## Canonical URL Index

- Homepage / Sound Meter: https://freesoundmeter.com/
- Decibel Meter & Charts: https://freesoundmeter.com/decibel-meter/
- About Free Sound Meter: https://freesoundmeter.com/about-us/
- Contact & Acoustic Inquiries: https://freesoundmeter.com/contact-us/
- Privacy Policy: https://freesoundmeter.com/privacy-policy/
- Terms and Conditions: https://freesoundmeter.com/terms-and-conditions/
- XML Sitemap: https://freesoundmeter.com/sitemap.xml
- Full LLM Documentation: https://freesoundmeter.com/llms-full.txt