The perception of decibel (dB) reduction and sound

Understanding how sound levels and decibel (dB) reductions are perceived is crucial to assessing the effectiveness of soundproofing and sound-absorbing measures. Decibels are a logarithmic unit, which means that a change of, for example, 10 dB does not correspond to a linear reduction in sound level, but rather a significant difference in perception.

To put this into perspective, a reduction of 3 dB corresponds to a halving of the sound's effect in purely physical terms, but human perception of sound works differently. A reduction of 10 dB is perceived as the sound being halved in strength, while a reduction of 20 dB often feels like the sound has been reduced to a quarter.

The perception of sound attenuation is also affected by the type of sound source being treated. A steady, low-frequency noise, such as engine noise or ventilation systems, may require a greater reduction in decibels for the difference to be clearly noticeable. On the other hand, sudden or high-frequency sounds, such as voices or sharp sounds from metal, can be perceived as more significantly dampened even with smaller reductions in decibels.

Sound-absorbing and sound-insulating materials play an important role in reducing noise levels and improving the acoustics in a room. By using sound absorbers in strategic locations, reverberation and reflections can be reduced, resulting in a quieter and more controlled sound environment. In some cases, it is a matter of combining different methods, for example by using both sound insulation to block sound transmission and sound absorption to reduce reflections within the room.

It is also important to understand that the sound experience can vary depending on the size and design of the room. In large open spaces, even a small change in sound level can make a big difference, while confined spaces with hard surfaces may require more extensive measures to achieve the desired effect.

In the text below, we go through various aspects of how decibel reduction is perceived, what affects sound perception, and how different measures can be used to optimize the sound environment in different types of environments.

From barely noticeable to almost inaudible: How we perceive attenuation in decibels

-1 dB to -3 dB
These changes are small and may be difficult to notice in many situations, especially in an environment with background noise.

-4 dB to -6 dB
Still small, but potentially noticeable changes, especially in a quiet environment or in a controlled listening situation.

-7 dB to -10 dB
A reduction of 10 dB is usually perceived as the sound becoming half as loud. So, in this range, the changes start to become clearly noticeable.

-15 dB
The sound is perceived as significantly quieter. Music or speech may become difficult to distinguish in a normal environment.

-20 dB to -30 dB
These are large reductions in sound level that can make the sound very quiet or even inaudible, depending on the initial sound level.

-35 dB to -40 dB
At these levels, most sound sources become extremely quiet. Background noise in a normal environment may drown out the sound source.

-45 dB to -50 dB
Sounds at these levels can be almost impossible to perceive without actively listening for them in a very quiet environment.

-55 dB
Reducing by another 5 dB from -50 dB makes the sound even quieter, and it may be virtually impossible to hear any sound at all from the sound source in a normal environment.

How are changes in sound levels perceived?

Sound levels are measured in decibels (dB), and small changes can have a big impact on how we perceive sound. Although a change of a few decibels may seem insignificant on a scale, it can have a noticeable effect in certain environments. Here we look at how changes in sound levels affect our hearing and when they become noticeable to the human ear.

Sound levels are measured in decibels (dB), and small changes can have a big impact on how we perceive sound. Although a change of a few decibels may seem insignificant on a scale, it can have a noticeable effect in certain environments. Here we look at how changes in sound levels affect our hearing and when they become noticeable to the human ear.

Small changes that can be difficult to perceive
A decrease of between -1 dB and -3 dB is generally very subtle. The change is often barely noticeable in environments where there is background noise, such as in an office, a restaurant, or outdoors. For this level difference to be clearly perceived, a quiet environment or a rapid change in sound is often required.

When the sound level decreases by -4 dB to -6 dB, the change becomes slightly more noticeable, especially in a quiet environment or in a controlled listening situation. In a recording studio or an acoustically optimized room, for example, this change may be easier to identify, but in everyday environments it can still be relatively difficult to distinguish.

Clearly noticeable changes in sound level
At a reduction of between -7 dB and -10 dB, the sound level begins to be perceived as significantly lower. The human ear interprets a reduction of 10 dB as the sound being halved in intensity. This means that if a conversation was previously perceived as being at a normal volume, it may now sound more muffled and distant. For music and speech, the difference becomes clear, and ambient noise may begin to dominate over the sound source.

At -15 dB, the sound level is reduced to such an extent that it can be difficult to distinguish details in both music and speech. In a quiet environment, the sound source can still be heard, but in an environment with background noise, it can disappear into the surroundings.

Significant reductions in sound level
When the sound level drops to -20 dB to -30 dB, the sound becomes significantly weaker. It can now be challenging to perceive speech and music, especially if the sound is not played close to the listener. In a noisy environment, the sound can almost completely disappear, while in a very quiet room it may still be audible, but with greatly reduced clarity and strength.

At -35 dB to -40 dB, sound sources begin to be extremely muffled. Sounds that were previously clear may now be difficult to perceive, and ambient sounds, such as ventilation, computer fans, or traffic outside, may completely take over. Hearing sounds at this level often requires active listening and a quiet environment.

Almost inaudible sound
When the sound level is reduced to -45 dB to -50 dB, it is very difficult to perceive the sound source, especially in environments where there are other sounds. Only in completely soundproofed spaces, such as recording studios or specially designed quiet rooms, can sounds at this level be audible.

At a reduction of -55 dB or more, the sound becomes virtually inaudible. If there is any background noise in the room, it will completely drown out the sound source. Only in extremely quiet environments, such as specially built anechoic chambers, can sound at this level still be perceived.

The impact of sound changes on our hearing
Sound level changes are perceived differently depending on the environment and surrounding noise. A reduction of 1–3 dB is barely noticeable, while a change of 10 dB makes the sound seem half as loud. When the sound level decreases by 20 dB or more, it becomes increasingly difficult to distinguish the sound source, especially if there is background noise. At reductions of 50 dB or more, the sound is so faint that it becomes practically inaudible to most people.

By understanding how decibel changes affect hearing, you can adapt sound environments to create better acoustic conditions. Whether you want to improve sound comfort in an office, optimize the acoustics in a home, or fine-tune sound levels in a recording studio, knowledge of sound level changes is an important part of sound planning and noise control.

Did you know that..

A reduction in sound level of 10 dB is perceived as the sound being halved, but in reality the physical energy of the sound has been reduced by as much as 90%? Many people believe that decibels work on a linear scale, but because decibels are a logarithmic unit, the change in sound volume is much greater than the numbers suggest.

Our ears are not equally sensitive to all frequencies, which means that some sounds are reduced more noticeably than others. Low-frequency sounds—such as traffic noise or dull thuds—may require a reduction of more than 15 dB to be noticeable, while high-frequency sounds—such as sharp voices or clinking glass—may feel halved at a reduction of just 5–7 dB.

The human ear can adapt to a change in sound, which means that a reduction of 3–5 dB may feel significant at first but then be perceived as less over time. This is why some noisy environments still feel loud despite sound insulation – we get used to the sound level and only notice the difference when we leave the room and come back.

So next time you're wondering how much soundproofing you need, remember that it's not just about the numbers on a measurement, but how our ears actually interpret the sound. And sometimes a small change can make a much bigger difference than you think!