Noise protection

Why protect against noise?

Noise is perceived subjectively. Music that we like will not sound as loud as a genre that we aren't too keen on, even if they are both played at the same volume. High notes are perceived as louder than low notes. Colours also influence our perception of noise. For example, our minds perceive red cars to be louder than green ones (source: TU Munich, in Die Zeit, 19 August 2004).

When it comes to noise protection, cutting corners is never a good idea, as attempting to reduce noise retroactively is usually difficult and requires a high financial outlay. You can save yourself the hassle and cost with good planning.

Effects

Objectively speaking, noise is harmful to health. The estimated cost to the economy is enormous. Depending on the sound pressure level, noise can cause the following negative effects:

Communication and concentration problems
Learning and performance difficulties
Disturbed sleep
Stress and long-term anxiety
Headaches
Cardiovascular problems
High blood pressure
etc.

But there are many other reasons for why noise protection must be given high priority during the construction of a building. These include:

Protecting privacy
Complying with laws and standards
Preserving or even increasing the value of a property
Ensuring undisturbed living even in densely built environments
Improving quality of life
etc.

What is sound?

Sound is a mechanical wave that propagates through space as the vibrations of a gaseous, liquid or solid medium. It is particularly audible in the human hearing range at vibration frequencies from 16,000 to 20,000 Hz.

In physical terms, sound that hits our ears is a vibration of air molecules that leads to small pressure fluctuations on and around the ear. The intensity of the sound is therefore influenced by the changes in air pressure.

Since these cover a large range from one to a billion, the sound level is commonly expressed on a logarithmic scale with the unit "decibel" (dB). The two most important characteristics of sound are sound pressure (loudness) and frequency (pitch). A frequency of less than 16 Hz is referred to as infrasound, while a frequency greater than 20,000 Hz is called ultrasound. Sound propagates through the air at a velocity of 340 m/s. This speed can vary greatly depending on the medium. Table 1 shows how well different media conduct sound.

Wood, for instance, is an excellent conductor of sound. This underlines the importance of noise protection measures in timber construction.

Material	Density (kg/m3)	Propagation velocity (m/s)
Air (20 °C)	0	344
Air (-20 °C)	0	319
Rubber	900 – 1’200	50
Cork	200 – 350	430 – 530
Concrete	2’300 – 2’500	3’700
Wood along the grain	300 – 900	3’500 – 5’000
Steel	7’850	5’000
Glass	2’400 – 2’600	5’000 – 6’000

Table 2 shows the sound levels of everyday sources of noise. A conversation from a distance of one meter is already perceived as being loud! As mentioned, our perception of noise is subjective and depends on how loud the background noise is. Nevertheless, it can generally be said that, above 40 dB, an increase or decrease in the sound level by 10 dB will be perceived as the volume either doubling or halving. While a difference in sound level of 3 dB is still perceptible, a difference of 1 dB is barely audible.

Sound source	Distance	Noise level	Feeling
Absolute silence		0 dB	Unpleasant
Ticking of a clock		20 dB	Barely audible
Residential area with no traffic		40 dB	Moderate noise
Car	10 m	60 dB	Loud noise
Conversation	1 m	70 dB	Loud noise
Car horn	5 m	100 dB	Very loud noise
Aeroplane taking off	10 m	130 dB	Intolerable noise

Nico to know!

People don't hear everything equally well. The audibility threshold hits its minimum at between 2,000 and 4,000 hertz. This is the frequency range at which sounds can be heard most easily.

Sources of noise

At home and in the workplace, noise pollution can come from both inside and outside of the building.

Poor room acoustics can also contribute to noise pollution. Hard surfaces reflect sound particularly well, causing the common problem of reverberation. We can divide the topic of "noise protection" into four areas according to the different sources of noise.