Psychoacoustics .

Psychoacoustics is the scientific study of sound perception. More specifically, the psychological and physiological responses associated with sound.

Hearing can be described as a sensory and perceptual occurrence. When a person hears something, it is not only perceived as a sound wave, but things called neural action potentials are produced. These nerve pulses travel to the brain where they are perceived. The inner ear processes signals to convert sound wave forms into neural stimuli so different types of wave forms may be imperceptible (wikipedia.com)

Sound Pressure Level and Loudess

Sound reaches the human ear in waves of pressure varying in time, s(t). This pressure is defined as force per unit area, and the unit in MKS system is Pascal (Pa) where 1 Pa = 1 N/m squared. The intensity is defined as power per unit area and its unit is W/m squared. Values of sound pressure vary from 10^-5 (absolute threshold of hearing) to 10 squared (threshold of pain) (sfu.ca)

Hearing Range and Threshold in Quiet

Hearing can range from 0 dB to 120 dB SPL. Human speech ranges from about 100 Hz to 8 kHz, which is what we can hear the best. Frequencies that fall below the threshold in quiet are insignificant to our perception of sound and are unnecessary to be processed (ucl.ac.uk)

Hearing Changes in the Harbor Porpoise

In 2016 the Journal of the Acoustical Society in America published an article devoted to the conditioned hearing sensitivity change in the harbor porpoise. It talks about an experiment that was carried out by a team of scientists where they played loud noises at different decibel levels and measured the temporary threshold shift (TTS) in the porpoises after each. They observed that the porpoise's TTS's ranged from about 4 kHz to 8 kHz. This means that by some psychophysical method the porpoises were able to shift their hearing threshold temporarily to protect their hearing. (asa.scitation.org)

Auditory Habits of Cope's Gray Treefrogs

A study done by scientists at the University of Minnesota was designed to better understand the role that mating calls play in the reproductive habits of Cope's gray treefrogs. Their hypothesis was that distance and consistency of pulse would determine the female's willingness to migrate. When a male treefrog emits a mating call, it pulses which creates the "ribbiting" sound. If the pulses are not consistent, the females will be less willing to mate. Scientists played two different calls; one at a short distance with consistent tone in the pulse, and one where every 5 pulses were played at different frequencies in different areas. The researchers found that the females were were more attracted to the lower frequency pulses, but also the shorter distance. (Bee, Schrode)

Psychoacoustics and Detection Theory

The Detection Theory is a "means of quantifying" (wikipedia.com) those who can discern between an informational audial pattern and noise. The theory states that there are a number of factors involved in being able to identify the pattern and where its threshold levels will be. It also states that affecting the threshold levels will inhibit the subject's ability to distinguish between the two. For example, a soldier in wartime might be able to detect weaker patterns than he would at peace due to heightened awareness, however he will be much more paranoid (cns.nyu.edu)

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Created with images by Jon_Callow_Images - "Wave"

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