Noise Basics and Metrics

In this section, you will learn about noise, including:

The basics of sound
Sound perception and hearing

In addition, you will learn about

Efforts that have been undertaken to reduce noise
Regulations from the Federal Aviation Administration aimed at reducing noise
Regulatory guidance for planning for noise compatible land uses on and around airports

Finally, this section will discuss models and metrics used to measure noise and the impact of weather on aviation operations.

First and foremost, it is important to understand what is noise. This is discussed inthe following section.

What is Noise?

Noise can be defined as any unwanted sound. What sounds annoy you may or may not annoy someone else. In addition, what sounds annoy you can vary, depending on the situation.

Here are some things that affect your level of annoyance:

Time of Day – For example, you may be more upset by noise heard at night while you are trying to sleep or relax, than from the same noise heard during a busy day at work. Noise at night may also be more noticeable because the background noise level is lower than during the daytime.
Length of Time – The longer you are exposed to a noise, the more it may annoy you.
Predictability – If you cannot predict when the noise will occur, it may annoy you.
Control – If you have little control over the noise, it may annoy you.
Emotional Variables – Emotional noise variables are those that cause differences in your perception of a noise. It depends on your experiences, values, beliefs, and mood. If you believe that a noise is unnecessary or unimportant, you may be more annoyed by the noise. For example, if you were awakened by noise from an airplane that you believed was transporting tourists, you could be irritated. On the other hand, if you knew the airplane was transporting goods such as food, medicine, mail, and other perishable necessities, you may be more willing to tolerate the disturbance.
Physical Surroundings – Surroundings such as snow, grass, trees, and other vegetation can help alleviate noise by reducing the sound through absorption or deflection of sound waves. However, during the summer months, open windows and more time spent outside may expose you to more noise.

Many variables influence people’s perception of noise. However, since the level of annoyance changes from person to person, it is difficult to determine what is too noisy or annoying for an entire community. This extremely complex human response to noise makes noise impact assessment a challenging task.

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