Frequency: 125 Hz

Wavelength: 2.74 m

Source Side → Wall Assembly → Receiver Side

Transmission

📊 Real-Time Frequency Response

🎚️ Frequency Control

125 500 1000 2000 4000

Transmission Loss (dB)

Deficiency (dB)

⚠️ Mass-Air-Mass Resonance Zone

At 125 Hz, the wall assembly experiences mass-air-mass resonance. Sound waves "punch through" more easily, creating significant deficiencies.

🔊 Real-World Sounds at This Frequency

Bass sounds in music, traffic rumble, HVAC systems, large machinery, thunder, building vibrations

📐 Acoustic Field Explanation

At low frequencies near resonance, the wall's mass and the air cavity form a coupled system. Sound pressure waves bounce between gypsum faces, creating standing wave patterns that efficiently transfer energy through the assembly.

Animation Speed

Incident

Transmitted

Reflected

Absorbed

NOAL 25-12001 • STC 42

Sound Demo Experience

Experience how sound energy is reduced as it passes through the wall assembly. Select a frequency, then listen to the source and transmitted tones.

Source Room

Receiving Room

Transmission Loss

26 dB

STC 42 Assembly

dB Source

dB Received

125 Hz — Bass / Low Frequency

Think: bass guitar, HVAC rumble, traffic noise. This wall reduces this frequency by 26 dB.

What is Transmission Loss?

Transmission Loss (TL) measures how much sound energy is blocked at each frequency. A 10 dB reduction sounds roughly half as loud. This wall's TL varies from 26 dB at low frequencies to 55 dB at high frequencies.

Why Frequency Matters

Low frequencies (bass) are hardest to block — they have long wavelengths that pass through materials more easily. That's why this wall shows only 26 dB TL at 125 Hz but 55 dB at 4000 Hz.

This Assembly

3 layers of 5/8" Type X gypsum on steel studs with glass fiber insulation. The mass, decoupling, and cavity absorption work together to achieve STC 42 performance.

Click to Begin
Audio Experience

Sound Transmission Lab

🔊 Sound Wave Propagation Simulation

🎚️ Frequency Control

⚠️ Mass-Air-Mass Resonance Zone

🔊 Real-World Sounds at This Frequency

📐 Acoustic Field Explanation

Sound Demo Experience

125 Hz — Bass / Low Frequency

What is Transmission Loss?

Why Frequency Matters

This Assembly

Click to BeginAudio Experience

Sound Transmission Lab

🔊 Sound Wave Propagation Simulation

🎚️ Frequency Control

⚠️ Mass-Air-Mass Resonance Zone

🔊 Real-World Sounds at This Frequency

📐 Acoustic Field Explanation

Sound Demo Experience

125 Hz — Bass / Low Frequency

What is Transmission Loss?

Why Frequency Matters

This Assembly

Click to Begin
Audio Experience