What is noise?
You hear noise. You are a victim of noise. But what is noise really? How is it measured? What are the effects of noise on your health and your environment? How can you reduce it? Here are some definitions to help you better understand how the Quietys anti-noise solution beats noise pollution.
Low frequency
Low frequency (LF) refers to the frequency band that ranges from 20 Hz (the lower limit of human hearing) to 700 Hz or 1 kHz. Low frequencies may be handled with active control.
Noise
Noise is a vibration that propagates through the air. It becomes bothersome when its nature, frequency or intensity is such that it causes problems for people, harms people’s health or has an adverse effect on the environment.
Active control
Active control is a noise reduction technique that uses auxiliary noise sources to counteract noise. Filing the first patent for noise reduction in 1934, inventor and physicist Paul Lueg is considered the father of this approach. Noise is a variation in pressure. If an auxiliary wave (also known as secondary wave) emits a pressure wave (noise) with the same amplitude, but with the opposite phase of the undesired noise, the two pressure waves are superimposed and cancel each other to create silence. In practical terms, this results in noise reduction. The advantages of active control over passive control include:
- Greater efficiency for handling low frequencies
- Smaller footprint and lower weight
- Selective handling ability
Recent progress in microelectronics and computer science has made it feasible and realistic to use this innovative technique to reduce noise pollution.
Passive control
Passive control relies on the use of specific materials that minimize the transmission of acoustic waves out into the environment. Materials used for passive control have absorbing, insulating and/or anti-reverberating qualities that reduce noise, particularly high pitched sounds. This approach is mainly used for handling high- and mid-range frequencies. Covering lower frequencies with passive control requires using materials of such thickness that they are frequently incompatible with industrial constraints.
Frequency
Frequency refers to the number of times that a periodic phenomenon repeats itself over a given time period. If seconds are chosen as the unit of time, then frequency is measured in Hertz (abbreviated as Hz), named after the physicist Heinrich Hertz.
Medium and high frequencies
Medium and high frequencies refer to the frequency band above 1 kHz. Passive control (with absorbing materials) is generally used to handle frequencies in this range.
Noise level
Noise level is measured in decibels. A decibel (dB) corresponds to the smallest acoustic pressure that can be detected by the human ear. To take the real level perceived by the ear into account, “physiological” decibels are used, referred to as A decibels and abbreviated as dB(A).
Noise pollution
Noise pollution includes all types of sound nuisance that are caused by various sources. Its consequences range from temporary discomfort to serious impact on your health and quality of life. Noise pollution can even have an adverse effect on ecosystem operation. Consequences for people include:
- Hearing fatigue
- Deafness (light, moderate, serious, irreversible)
- Stress, irritability
- Performance loss for workers carrying out cognitive tasks
- Increased risk of work-related accidents
- Cardiovascular problems, altered blood pressure
- Sleep troubles, insomnia
- Depression
- Difficulty with oral communication at work
- Physical and nervous fatigue