Noise

Noise is sound we do not want.

It can be loud and annoying.

Sound moves through air or water. This happens with tiny shakes called vibrations. When these shakes reach our brain, we hear them.

We can measure how loud a sound is. People use a tool called a meter. A soft voice is quiet. A rock concert is very loud.

Too much noise can be bad. It can hurt our ears. It can also stop us from sleeping.

Cars and planes make a lot of noise. We can use walls to block it. This helps keep us safe and calm.

Noise is sound that we find unwanted or harmful.

Science tells us that all sound is just vibrations. These vibrations move through things like air or water. The difference between music and noise happens in our brains.

We can measure sound in two main ways. First, we measure loudness. We use decibels, or dB, to show how much power a sound has. A normal voice is about 65 dBA. A rock concert can reach 120 dBA. Second, we measure pitch. Pitch is the frequency of a sound wave. We measure this in hertz, or Hz.

People use a Sound Level Meter to study these numbers.

Too much noise can cause health problems. It can lead to hearing loss or high blood pressure. It can also stop people from sleeping well. Many sounds come from cars, trains, and planes. This is called noise pollution. To help, governments make rules to limit loud sounds. We can also use noise barriers to block the sound.

Noise is sound that people find unwanted or harmful. In physics, there is no real difference between noise and music. Both are just vibrations moving through a medium like air or water. The difference only happens when a brain hears and perceives the sound. Some noise is accidental, like a hiss in an electronic signal. Other noise is made on purpose, like white noise.

Scientists measure sound using two main ideas. They look at amplitude, which is how forceful a wave is. This loudness is measured in decibels, or dB. They also look at frequency, which is the pitch of a sound. This is measured in hertz, or Hz. A Sound Level Meter is the main tool used to measure air sounds. People also use Noise Dosimeters to check noise in workplaces.

Measuring sound can be very specific for human hearing. Experts use a method called A-weighting to represent what humans hear. This makes the measurement decibels A-weighted, or dBA. A very soft sound is 0 dBA. A normal human voice is about 65 dBA. A loud rock concert can reach about 120 dBA.

Too much noise can cause real health problems for people. This is often called noise pollution. It comes from things like cars, trains, and planes. Constant loud noise can cause hearing loss or high blood pressure. It can even cause heart disease or trouble sleeping. In the United States, the Noise Control Act was passed in 1972. This law helped protect people from noise that threatens health.

Governments use many rules to keep noise levels safe. In the United States, the EPA studies how noise affects us. The group NIOSH suggests a limit of 85 dBA for an 8-hour workday. If the noise gets louder, the time spent listening must be shorter. In Europe, the European Environment Agency also regulates noise. They even look at underwater noise to protect the ocean.

Noise is often defined as unwanted, unintentional, or harmful sound. It is considered unpleasant or disruptive to a person's mental state or hearing. From a purely physical standpoint, scientists see no difference between noise and desired sounds like music. Both are simply vibrations traveling through a medium, such as air or water. The distinction only occurs when a brain receives and perceives the sound in a specific way. This perception turns a simple vibration into something categorized as noise.

To understand noise, we must look at how sound waves function. Sound is measured by two primary characteristics: amplitude and frequency. Amplitude describes how forceful a sound wave is. This intensity is measured in decibels (dB) using a logarithmic scale. Frequency describes the pitch of the sound and is measured in hertz (Hz). The most common tool for measuring sound in the air is the Sound Level Meter. In specific settings, experts use different tools for different jobs. Noise Dosimeters are used in occupational environments to track exposure. Noise monitors track environmental noise, while some people even use smartphone apps to map community noise.

Because human hearing is not equally sensitive to all frequencies, scientists use a special filter. This is called A-weighting, which adjusts the sound spectrum to represent what humans actually hear. When this filter is applied, the measurement is expressed in decibels A-weighted, or dBA. This scale allows for a standardized way to discuss loudness. For example, 0 dBA is the softest level a person can hear. A normal human speaking voice is approximately 65 dBA. In contrast, a loud rock concert can reach about 120 dBA.

Noise can appear in many different forms depending on the field of study. In audio engineering, noise refers to unwanted residual signals. These can be acoustic, such as sounds from loudspeakers, or electronic, which often sound like a hiss. There are four major types of audio noise: hiss, rumble, crackle, and hum. These can be caused by recording equipment, the instruments themselves, or the room. In experimental sciences, noise refers to random fluctuations in data. These fluctuations can make it difficult for researchers to perceive a specific signal.

Environmental noise is the total accumulation of all noise in a specific area. Major sources include aircraft, trains, industrial sites, and motor vehicles. This buildup is often called noise pollution. High levels of noise pollution can lead to significant health consequences. These include hearing loss, cardiovascular disease, and high blood pressure. It can also cause sleep disturbances, injuries, and decreased school performance. Even psychological effects, such as annoyance and psychiatric disorders, are linked to noise.

To protect public health, many governments have established noise regulations. In the United States, the Noise Control Act was passed in 1972. This act aimed to promote healthy living and establish federal standards for commercial products. The Environmental Protection Agency (EPA) was authorized to study noise and evaluate regulations. In the workplace, the National Institute for Occupational Safety and Health (NIOSH) provides safety recommendations. They set a recommended exposure limit (REL) of 85 dBA for an 8-hour workday. This limit uses a 3-dB exchange rate. This means if the noise increases by 3 dB, the allowed exposure time must be cut in half. For instance, at 88 dBA, a worker should only be exposed for 4 hours.

Regulation and mitigation strategies exist to reduce these risks. Strategies include land-use planning, noise barriers, and sound baffles. In Europe, the European Environment Agency regulates noise through the Environmental Noise Directive. This directive aims to increase public access to information and reduce environmental noise. They even regulate underwater noise as a pollutant under the Marine Strategy Framework Directive. While noise-induced hearing loss is permanent, it is often preventable through these rules and proper hearing protection.