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When discussing the reduction of sound vibration as it travels from one side of a wall to the other, we need to quantify and measure this loss. Do all construction techniques or soundproofing materials work equally well? Exactly how much sound is being reduced, and perhaps more importantly, what frequencies of sound are being affected? This is where understanding STC (Sound Transmission Class), and STC ratings, comes in.

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We see two walls, one has an STC 47 (4″ Solid Concrete), the other an STC 48 (Steel Stud Wall). Note that in the low-frequency range – important for music, theaters, traffic, aircraft, and most other real-world noise sources – the lower STC wall is literally 30 decibels better, yet lower STC.

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Higher STC ratings generally are better. However, don't forget that STC ratingsonly take into account sounds over 125Hz. This means that extremely low frequencies don't register on the STC rating scale, thus when a sound on one side of a wall is below 125Hz, the ability of the wall to block sound cannot be calculated.

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"an effect whereby the sound produced by an amplifier or an amplified musical instrument is made to reverberate slightly."

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"Room acoustics is the broad term that describes how sound waves interact with a room. Each room, and all the objects in it, will react differently to different frequencies of sound. Every speaker will sound different in different rooms."

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"Sound Transmission Class (or STC) is an integer rating of how well a building partition attenuates airborne sound."

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"Sound pressure level is measured in units of decibels (dB) and is calculated using the following equation, where p is the sound pressure of the sound wave and po is the reference sound pressure"

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"Sound pressure level uses a logarithmic scale to represent the sound pressure of a sound relative to a reference pressure. The reference sound pressure is typically the threshold of human hearing: remember that it's 2 x 10-5 Pa."

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The filters used for dBA and dB(C) The most widely used sound level filter is the A scale, which roughly corresponds to the inverse of the 40 dB (at 1 kHz) equal-loudness curve. Using this filter, the sound level meter is thus less sensitive to very high and very low frequencies.

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The filters used for dBA and dB(C) The most widely used sound level filter is the A scale, which roughly corresponds to the inverse of the 40 dB (at 1 kHz) equal-loudness curve. Using this filter, the sound level meter is thus less sensitive to very high and very low frequencies.

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"Sound pressure is the pressure measured within the wave relative to the surrounding air pressure. Loud sounds produce sound waves with relatively large sound pressures, while quiet sounds produce sound waves with relatively small sound pressures.