How does mass affect sound isolation?

According to the mass law, doubling the mass of a wall increases sound isolation by approximately 6 dB. A single-leaf brick wall (200 kg/m²) provides about 45-50 dB isolation at 500 Hz. Adding mass is the most predictable way to increase isolation.

What STC/Rw rating do I need for a studio?

Home studio: STC 45-55 (reduces loud music to faint background). Professional recording studio: STC 55-65. Broadcast studio: STC 60+. Drum room isolation: STC 65+. Each 10 STC increase roughly halves the perceived loudness transmission.

Is mass the only factor for sound isolation?

No. Decoupled double-wall construction (two separate walls with an air gap) can far exceed mass law predictions. The air gap acts as a spring, and adding absorption inside the cavity further improves performance. Flanking paths through floors, ceilings and ducts often limit real-world performance.

Why is bass so hard to isolate?

The mass law shows that isolation decreases by 6 dB per octave as frequency drops. A wall providing 50 dB isolation at 500 Hz only provides about 26 dB at 50 Hz. Bass wavelengths are also longer and can more easily diffract around barriers and travel through structural paths.

AudioCalcs

Isolation Calculator — Sound Transmission Loss

Calculate sound isolation (STC/Rw) from wall construction layers.

Source Sound Level

Wall Surface Mass

Frequency

How We Calculate This

Mass Law (single leaf)

TL = 20 × log10(m × f) − 47

Where m = surface mass in kg/m² and f = frequency in Hz. This is the field incidence mass law, an approximation that works reasonably well for single-leaf constructions away from coincidence frequency.

Transmitted Level

Transmitted = Source Level − TL

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard formulas. Always verify results for critical applications.