Sound level

Professional Definition

The sound level is the acoustic pressure level adjusted by the appropriate frequency characteristic (most often A, C, or Z), expressed in decibels. It is a measure that takes into account the nonlinear sensitivity of the human ear depending on the frequency of the acoustic wave.

From a technical point of view, the calculation of the sound level involves summing the energy levels of pressure in individual frequency bands after adding the correction values derived from the selected weighting curve. The most popular A curve (dBA) heavily suppresses low frequencies to mimic the hearing characteristics at low volume levels, while the C curve is used for impulsive and high-intensity noises.

Acoustics in Simple Words

Imagine that the raw acoustic pressure is the total sunlight coming into a room. The sound level is the image you see after putting on polarized sunglasses.

Our ears act just like such a filter – they naturally "dampen" very low bass and very high squeaks while sharpening the human speech range. If we measured noise without any correction, the result might suggest that the room is loud (because, for example, a powerful, slow-moving fan is running), while we would barely hear it. Therefore, the sound level is "noise converted to the human ear," allowing us to assess whether a certain sound will actually be bothersome to us.

Summary

The sound level is a fundamental concept in environmental protection and occupational health and safety, serving as a bridge between the physical phenomenon of the wave and the subjective perception of loudness. By applying corrective filters (A, B, C, D, or G), engineers can accurately determine the risk of hearing damage or the degree of annoyance caused by noise.