The Nature of Sound

This week we studied about sound.A vibration  is the complete back-and-forth motion of an object.
A sound wave is a longitudinal wave that is caused by vibrations and that travels through a material medium.
Sound waves travel in all directions away from their source.
However,air or the other matter does not travel in sound waves.The particles of air only vibrate back and forth.

If air did travel with sound,wind gusts from music speakers would blow you over at a school dance!
But in a vacuum there are no particles to vibrate.
So no sound can be made  in a vacuum.

The many parts of the ear must work together for you  to hear sounds.If any part of the ear is damaged
or does not work properly,hearing loss or deafness may result.
One of the most common types of hearing loss  is called tinnitus.

Conductive Hearing Loss

Conductive hearing loss is the result of disorders in either the outer or middle ear, which prevent sound from getting to the inner ear. Voices and sounds may sound faint, distorted or both.
Some common causes of conductive hearing loss:

• Infection of the ear canal or middle ear
• Fluid in the middle ear
• Perforation or scarring of the eardrum
• Wax build-up
• Dislocation of the ossicles (three middle-ear bones)
• Foreign objects in the ear canal
• Otosclerosis
• Unusual growths, tumors

• Sensorineural

  Hearing Loss

  Sensorineural hearing loss occurs when inner ear nerves become damaged and do not properly transmit their signals to the brain. Patients may complain that people seem to mumble or that they hear, but do not understand, what is being said. The aging process is the most common cause of sensorineural hearing loss. As we get older, the inner ear nerves and sensory cells gradually die.
• If a hearing loss is the result of both conductive and sensorineural components, it is known as a mixed hearing loss.

Ways to prevent hearing loss
Pick the Right Earphones
In a noisy setting, the sound-isolating kind are best, says Brian Fligor, director of diagnostic audiology at Children's Hospital Boston: "They block the right proportion of high and low frequencies so you can hear your music at a lower volume." Noise-canceling headphones are less effective; they block mostly low frequencies.

Swallow Some Protection
Inside our ears lie thousands of hairlike cells that turn sound waves into electrical signals so the brain can interpret what we hear. But very loud noise generates free radicals that damage those cells—sometimes permanently. The U.S. military has been pouring money into research on prevention, and it's paying off. A clinical trial revealed that an over-the-counter supplement called N-acetylcysteine worked much better than earplugs alone at minimizing damage in Marines exposed to gunfire. Researcher Richard D. Kopke, MD, recommends taking 1,200 milligrams 12 hours before you're bombarded by loud noise (say, at a sporting event). If the noise is unexpected, pop 1,200 milligrams as soon as possible and take 900 to 1,200 milligrams three times a day, with meals, for the next 14 days.

PROPERTIES OF SOUND

Pitch a measure of how high or low a sound is perceived to be,depending on the frequency of the sound wave.

 

 

 

 

The doppler effect is the apparent change in the frequency of a sound caused by the motion of either the listener or the source of the sound.The same sound source is radiating sound waves at a constant frequency in the same medium. However, now the sound source is moving to the right with a speed υ_s = 0.7 c (Mach 0.7). The wave-fronts are produced with the same frequency as before. However, since the source is moving, the centre of each new wavefront is now slightly displaced to the right. As a result, the wave-fronts begin to bunch up on the right side (in front of) and spread further apart on the left side (behind) of the source. An observer in front of the source will hear a higher frequency , and an observer behind the source will hear a lower frequency

Species	Approximate Range (Hz)
human	64-23,000
dog	67-45,000
cat	45-64,000
cow	23-35,000
horse	55-33,500
sheep	100-30,000
rabbit	360-42,000
rat	200-76,000
mouse	1,000-91,000
gerbil	100-60,000
guinea pig	54-50,000
hedgehog	250-45,000
raccoon	100-40,000
ferret	16-44,000
opossum	500-64,000
chinchilla	90-22,800
bat	2,000-110,000
beluga whale	1,000-123,000
elephant	16-12,000
porpoise	75-150,000
goldfish	20-3,000
catfish	50-4,000
tuna	50-1,100
bullfrog	100-3,000
tree frog	50-4,000
canary	250-8,000
parakeet	200-8,500
cockatiel	250-8,000
owl	200-12,000
chicken	125-2,000