Acoustics | Fundamentals

 

Sound can be explained as pressure waves reaching our ears. Our hearing translates these waves into electrical signals to our brain.

When discussing sound, we make a distinction between frequency and decibels.

Frequency

Frequency is the number of waves (vibrations) a sound source emits per second. The amount of waves per second is expressed by the term hertz (Hz). The shorter the wavelength, the more vibrations per second. The more vibrations per second, the higher the frequency is, and with it the sound we hear.

The human ear detects sound in a frequency range of 20 Hz – 20.000 Hz. Most sounds around us however have a frequency between 100 Hz and 5000 Hz.


High frequencies
Short waves
250-2500 Hz | e.g. ringtones

Middle frequencies
Medium waves
250-2500 Hz | e.g. speech
  
Low frequencies
Long waves
50-250 Hz | e.g. ventilators

Frequency

Frequency is the number of waves (vibrations) a sound source emits per second. The amount of waves per second is expressed by the term hertz (Hz). The shorter the wavelength, the more vibrations per second. The more vibrations per second, the higher the frequency is, and with it the sound we hear.

The human ear detects sound in a frequency range of 20 Hz – 20.000 Hz. Most sounds around us however have a frequency between 100 Hz and 5000 Hz. 

Frequency

Frequency is the number of waves (vibrations) a sound source emits per second. The amount of waves per second is expressed by the term hertz (Hz). The shorter the wavelength, the more vibrations per second. The more vibrations per second, the higher the frequency is, and with it the sound we hear.

The human ear detects sound in a frequency range of 20 Hz – 20.000 Hz. Most sounds around us however have a frequency between 100 Hz and 5000 Hz.


High frequencies
Short waves
250-2500 Hz | e.g. ringtones

Middle frequencies
Medium waves
250-2500 Hz | e.g. speech
  
Low frequencies
Long waves
50-250 Hz | e.g. ventilators

It is important that the sound absorbing quality of an acoustic solution lies within the frequency range causing discomfort and distraction

Decibels

The loudness (volume) of sound is expressed by the term decibels (dB). The higher the number of decibels, the louder a sound is. The human ear can withstand a sound volume of 140 dB. Our pain threshold however starts already at 100 dB.

At offices background noise often reaches a level of 60 – 80 dB, whereas a maximum of 45 dB is advised. A space with too much noise greatly compromises speech intelligibility and the ability to focus. Soon it is perceived being uncomfortable, (unconsciously) impacting the health and wellbeing of the people inside.

 

Decibels

The loudness (volume) of sound is expressed by the term decibels (dB). The higher the number of decibels, the louder a sound is. The human ear can withstand a sound volume of 140 dB. Our pain threshold however starts already at 100 dB.

At offices background noise often reaches a level of 60 – 80 dB, whereas a maximum of 45 dB is advised. A space with too much noise greatly compromises speech intelligibility and the ability to focus. Soon it is perceived being uncomfortable, (unconsciously) impacting the health and wellbeing of the people inside.

Reverberation

Reverberation time is the amount of time it takes for a sound to fade away. Reverberation time is measured via a RT60-test, in which the seconds are timed it takes for the volume of a test sound to be reduced by 60 decibels. Next to volume, several other factors affect reverberation time, including the type of furniture and temperature. Introducing sound absorbing material into a space will bring down reverberation time.

The desired reverberation time is dependent on the intended purpose of a space. For an office for instance 0.8 seconds is advised. Meeting rooms however are generally fitted to have a reverberation time of 0.4 seconds.

Adding sound absorbing material to a space reduces reverberation time

Absorbing sound reduces the number of sound waves traveling distantly  (reverberation), thus increasing speech intelligibility nearby

Sound absorption

Sound induced distraction and discomfort may come from noise in an adjacent space, or from a disturbing sound source within a space. Our collection is designed to tackle the latter. Examples are noise created by loud conversations, or the sound coming from a printer or espresso machine. Thanks to their sound absorbing properties our luminaires lower these sounds to an acceptable level.

When sound is absorbed, energy from sound waves is partially ‘trapped’ in acoustic material. Depending on the material, the shape, and the surface structure, a part of the sound waves reflect back into space.

Absorbing sound reduces the number of sound waves traveling distantly  (reverberation), thus increasing speech intelligibility nearby