How Noise Affects People's Health

The World Health Organization (WHO) calls noise (colloquially also referred to as racket) the second-largest environmental hazard to physical and mental health in Europe. People exposed to loud or sustained noise often suffer from cardiovascular and metabolic diseases. Noise can also significantly affect performance and sleep, generally raise stress levels, and impair people's mental health. This can also permanently reduce quality of life through irritability, hearing impairment, and even tinnitus.

Definition: what exactly is noise?

Noise refers to any unwanted, usually loud sound. Ears pick up these sounds and process their information. The stronger the sound, the more people perceive it as unpleasant noise. Still, the concept of noise is shaped subjectively. Sounds from, say, a children's playground can be judged very differently — from negative to genuinely positive — depending on the listener and the situation they're in.

Incidentally, the German word for noise, "Lärm," originally comes from Italian and means "to arms" — "all'arme" is linked to the German word "Alarm" (alarm). In legal texts, there's a very simple definition of noise: it's simply "unwanted sound."

A distinction is made between continuous noise, intermittent noise, and impulse noise:

• Continuous noise comes, for example, from machines like pumps or blowers, and describes sounds that occur constantly over a longer period.

• The sounds of a plane taking off, or the air-Q's warning tone when it warns residents of carbon monoxide. This type of noise is called intermittent noise, since the sound level rises quickly and then drops again.

• Impulse noise, finally, is triggered by very brief events — such as an explosion or a bursting balloon.

Typical sources of noise are listed below. These result in different perceptual contexts and different noise effects:

• Road traffic noise, rail traffic noise, aircraft noise
• Commercial and industrial noise
• Construction site noise
• Neighborhood noise, leisure noise

Measuring noise: from the hearing threshold to the pain threshold

Measuring noise is only possible via the physically describable sound. Sounds arise from vibrations and propagate through the air as sound waves. Volume depends on the strength of the sound. What's measured is sound pressure, displayed as a sound pressure level in decibels. Every such sound event represents a tiny pressure fluctuation around atmospheric air pressure. These vibrations are captured by human hearing.

How disruptive a volume is perceived to be depends significantly on the sound pressure and its pitch. Generally, a sound pressure level of 120 to 140 decibels is described as the pain threshold. This is measured as frequency, meaning air pressure fluctuations per second, in hertz. If the frequency is high, human hearing also perceives the sound as higher-pitched. However, this complex organ perceives low and very high tones as less loud than mid-frequency tones. So tones of different frequencies can be perceived as equally loud at different sound pressure levels.

To account for this physiological fact, sound pressure level is measured using the A-weighting filter. This filter adjusts the measured sound pressure level to match human sound perception. The correction is based on the A-weighting curve, which adjusts sound levels with low and high frequencies downward, since these are perceived as quieter by human hearing. The resulting unit is dB(A). The air-Q air analyzer measures sound pressure level in the range of 30 to 109 dB(A) at a frequency of more than 200 hertz (see datasheet). The resolution is 1 decibel, with an accuracy of ± 2 decibels.

What noise thresholds apply in Germany?

To avoid health impairment, the World Health Organization has issued recommendations for maximum volumes. For longer-term noise levels, a threshold of 65 decibels during the day and 40 decibels at night applies. For comparison: the most important cause of noise in Germany is traffic noise from road, air, or rail traffic. More than one in three European residents is exposed to road noise of 55 decibels long-term. While noise from trains or other rail vehicles at night is perceived as relatively less sleep-disruptive, aircraft noise plays the biggest role here.

A separate regulation exists specifically for noise at the workplace, set out in the Noise and Vibration Occupational Safety Ordinance (LärmVibrationsArbSchV). The threshold varies depending on the type of activity, its duration, and the specific location. The volume of noise that occurs briefly (impulse noise) is also relevant. From the employer's perspective, taking certain protective measures is mandatory under a 2003 EU Parliament and Council directive:

• If an employee is exposed to a sound level of 80 dB(A), or impulse noise with a high sound pressure of 135 dB(C), over a longer period, the employer must provide information or instruction. The employer must provide hearing protection. (Lower exposure action value)

• If the employee is exposed to a sound level of 85 dB(A), or impulse noise of 137 dB(C), over a longer period, the employer must not only provide hearing protection but also monitor its use. (Upper exposure action value)

• Sound protection must be designed so that 87 dB(A), as the maximum permissible sound level during an eight-hour workday, isn't exceeded. For this, the exposure value is measured at the ear while hearing protection is worn.

Noise and its effects on well-being

Fundamentally, high sound peaks as well as continuous sound burden human hearing. The so-called hair cells of the inner ear can be significantly damaged by noise. This leads to impaired acoustic perception. The problem is that these hair cells don't regrow: noise-induced damage is therefore irreparable and can ultimately lead to hearing loss. Chronic or temporary ear ringing, such as tinnitus, is also possible.

The NORAH study, presented at the end of 2015, is considered one of the most comprehensive international studies to date on the effects of aircraft, rail, and road traffic noise on population health and quality of life. Nine renowned research and specialist institutions, including from the fields of social science, psychology, acoustics, and physics, joined forces to study noise, particularly in the Rhine-Main region.

The study confirms that all three types of traffic noise lead to elevated cardiovascular risks. A direct link between chronic noise exposure and depression was also established for the first time. The assumption that noise affects blood pressure, however, was not confirmed. More information on the NORAH study is available here.

‍Noise reduction: what's being done against excessive noise exposure?

City representatives and residents are increasingly facing off in court over high noise exposure. In Heidelberg, for example, there's a dispute over noise in the old town, concerning restaurant closing times — which, out of consideration for the city's large student population, are sometimes as late as 4 a.m. Residents had previously taken noise measurements and found unreasonable exposure levels. The administrative court had set a minimum of six hours of nighttime quiet — and the city has appealed; the outcome remains open.

In North Rhine-Westphalia, an action alliance called NRW wird leiser ("NRW is getting quieter") has formed, advocating, for example, for restricted usage times for conventional leaf blowers. Such leaf blowers, also controversial because they, for example, shred small animals, produce noise up to 91 dB(A) when standing within a three-meter radius. In Dorsten, leaf blowers may therefore only be used under very restricted conditions. It would be better if battery-powered alternatives were used instead.

Anyone who wants to know exactly what noise exposure they face in their home or workplace can get a measuring device like the air-Q, to visualize both short-term sound levels and longer-term sustained exposure.

(Image: Pixabay/ Alexey Chizhov)