What does noise affect?
- Noise Effects & Mitigation
- How does Noise affect People?
- How does Noise affect Domestic Animals and Wildlife?
- Other Noise Related Effects
Noise-Induced Hearing Impairment
Residents in surrounding communities often have real concerns regarding the effects of aircraft noise on hearing.
This section provides a brief overview of hearing loss caused by noise exposure. The goal is to provide a sense of perspective as to how aircraft noise (as experienced on the ground) compares to other activities that are often linked with hearing loss.
Definition of Hearing Impairment
Considerable data on hearing loss have been collected and analyzed by the scientific/medical community. It has been well established that continuous exposure to high noise levels will damage human hearing.
Hearing loss is generally identified as a decrease in the ear's sensitivity or ability to perceive sound. This is often described as a shift in the hearing threshold to a higher level. This change can be one of two types:
- Temporary Threshold Shift (TTS)
- TTS can result from exposure to loud noise over a given amount of time. Yet, the hearing loss is not necessarily permanent.
- An example of TTS might be when you attend a loud music concert. After the concert is over, you may experience a threshold shift that may last several hours. The length of time you are affected depends upon the level and duration of exposure.
- While experiencing TTS, you become less sensitive to low-level sounds. This particularly occurs at certain frequencies in the speech range. The range is typically near 4,000 Hertz. With enough time to recover within a relatively quiet environment, your normal hearing ability eventually returns.
- Permanent Threshold Shift (PTS)
- PTS usually results from repeated exposure to high noise levels. It occurs when the ears are not given adequate time to recover from the strain and fatigue of exposure.
- A common example of PTS is the result of working in a loud environment such as a factory.
- A Temporary Threshold Shift (TTS) can eventually become Permanent Threshold Sift (PTS) over time. Even if the ear is given time to recover from TTS, repeated occurrence of TTS may eventually lead to permanent hearing loss.
- The point at which a Temporary Threshold Shift results in a Permanent Threshold Shift is very difficult to identify. It also varies with a person's sensitivity. In general, hearing loss (be it TTS or PTS) is determined by the duration and level of the sound exposure.
It is unlikely that airport neighbors will remain outside their homes 24 hours/day for extended periods. Therefore, there is little possibility of hearing loss below a day-night average sound level of 75 dB. (Note that this level is extremely conservative.)
Non-Auditory Health Effects of Noise
- stress response
- blood pressure
- birth weight
- mortality rates
- cardiovascular health
Exposure to very loud noise can elevate blood pressure and also stress hormone levels. This response is typically seen for much higher noise levels than those produced by aircraft in the community. The response to such loud noise is typically short in duration. After the noise stops, the physiological effects reverse and levels return back to normal.
In the case of repeated exposure to aircraft noise, the connection is not as clear. The results of most cited studies are uncertain and are often contradictory. In addition, too few studies have been done. A definite link between aircraft noise exposure and the various types of non-auditory health effects has not been found. Click here for a brief description of the findings from a few studies.