Last update: 19.08.2019
Sound control
4.

Sound wave characteristics

Noise is a mixture of different sound waves that arise in solid compounds, liquids or gases (air). Depending on the way they are transmitted, these waves are known as airborne or structure-borne noise.

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Noise is a mixture of different sound waves that arise in solid compounds, liquids or gases (air). Depending on the way they are transmitted, these waves are known as airborne or structure-borne noise.

Airborne sound

Airborne sound

 

Structure borne sound

Structure borne sound

 

Limits

Sound is normally transported through both air and solid objects. The intensity of pressure fluctuations is called sound pressure, measured in Decibels (dB), and can vary significantly from the ticking of a clock to the crack of a gunshot.

Decibel meter

 

Sound source

Frequency is the number of waves or vibrations per second and is measured in Hertz (Hz). Sound or noise is composed of many waves of different frequencies. Deep tones represent low frequencies and high tones high frequencies.

Sound pressure

 

Sound perception – Sound rating

The mix of these frequencies in a sound can be represented as a frequency spectrum. The fre- quency spectrum of sounds that the human ear can hear falls between 20 and 20,000 Hz. Only the highest range, which lies at around 4 kHz and then dissipates rapidly in both directions, is relevant when it comes to protecting against structural noise. Sound insulation ratings, therefore, primarily take the range between 100 and 5,000 Hz into account. Moreover, as the human ear registers high frequencies more readily than low frequencies, appropriate consideration is taken of this auditory sensation, a capacity which is expressed in terms of dB(A), where “A” stands for adjusted in this respect. Defining sound reduction does not follow a linear path, but is a logarithmic function. For example, two sources of sound that are each 80 dB do not add up to 160 dB, but only to  83 dB. Therefore, the human ear registers a difference of ± 10 dB as a doubling or halving of the volume.

Generally, the following ratings apply based on a logarithmic correlation:

Sound perception correlation


Since a large percentage of sound insulating glass installed today is rated for 40 dB, this type of glass only permits around 6 % of external noise to penetrate to the inside of a building.