A Guide To Stc Noise Measurement Criteria

By Author: Kevin Richard
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Not all noise is of the same type. In the din or urban living, undesired sound may vary from the loud thud of heavy machinery to high pitch sirens of a passing police car. How much transmission of sound is permitted by the wall? Can a single number measure all of them?

In this post, we will discover some misconceptions behind the STC noise measurement criteria, which are generally utilized in acoustic treatment and soundproofing.

What is Sound Transmission Class (STC)?

STC stands for Sound Transmission Class. Before we can realize how it works, we have to look at some other terms.

First of all, let us look at dB or decibels. A dB value just measures how soft or loud a sound is. A loud rock band at a club is generally around 100 dB, while the noise level in a quiet office is possibly around 30 dB.

While sound proofing door, wall or window, this dB value can be impacted. The reduction in this value is known as loss of transmission. For instance, imagine we are at the same club where ...
... noise levels are measured to be as loud as 110 dB. After closing the door of the club and standing outside, the meter reads 90 dB. We can then say that the walls, door and other associated components of the club has caused in the loss of transmission by 20 dB in general.

But wait a minute! I can still hear the loud bass wobble and kick drum, although the guitars will hardly make out. If we sent a pure sine wave through the same door and changed frequency every time, we will find that the transmission loss value is different in every case.

This implies that transmission loss depends on the frequency measured. Frequency is measured in Hz. The loud boom of the kick drum was possibly between 20 Hz and 60Hz, while the now inaudible guitars were possibly 500 Hz. The human ear is able to identify sounds ranging from 20 Hz to 20,000 Hz.

By taking 16 standard frequencies from 125 Hz to 400 Hz and adhering to the STC noise measurement criteria, a curve may be plotted. There are various standard reference curves. If the plotted curve matches an STC 45 curve, then that structure or wall being tested is said to have a STC of 45.

Some workplaces are noisier than others. We can make everything silent, nonetheless we can get ways to reduce the noise in the design of the buildings.

Conclusion

As we can see, STC are reference curves to assist us decide how well a wall prevents sound from being transmitted into another room. Noise Criterion, in both NCB and NC variants are reference curves that assist us to access the noise that is present in an ambiance or room. Determining these values are important in devising a quiet barrier HD and noise control solutions.