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  1. SOUND

  2. SOUND Vibrations that travel through air or another medium and can be heard when they reach a person’s or animal’s ear is defined as sound .


  4. 1. Megaphones and musical instruments Megaphones or loudhailers, horns, musical instruments are all designed to send sound in a particular direction without spreading it in all directions. In these instruments, a tube followed by a conical opening reflects sounds successively to guide most of the sound waves from the source in the forward direction.

  5. shehanai

  6. 2. In stethoscope the sound of a patient's heartbeat is guided by along the tube of the stethoscope to the doctor's ears by multiple reflections of sound.

  7. 3. Curved ceilings of concert halls, conference halls and cinema halls are made curved so that sound after reflection reaches all the corners of the halls.



  10. HEARING RANGE Hearing Range usually describes the range of frequencies that can be heard by an animal or human, though it can also refer to the range of levels. In humans the audible range of frequencies is usually said to be 20 Hz (cycles per second) to 20 kHz (20,000 Hz), although there is considerable variation between individuals, especially at the high frequency end, where a gradual decline with age is considered normal.

  11. HEARING RANGE IN HUMANS In a human, sound waves funnel into the ear via the external ear canal and hit the eardrum (tympanic membrane). Consequently the compression and rarefaction of the wave set this thin membrane in motion, causing the middle ear bones (the ossicles; malleus, incus and stapes) to move. The number of sound pressure level vibrations (sonic waves) per second denotes the frequency.Infrasonic (below hearing), sonic (aural), and ultrasonic (above hearing) frequencies are measured in Hertz (Hz); one Hertz is one cycle wave (or singular pressure wave in audionics) per second.

  12. Psychoacoustics. Humans have developed culture and technology such as music,telephone and radio . that allows them to generate, record ,transmit, and broadcast sound. The scientific study of human sound perception is known asPsychoacoustics.

  13. INFRASOUND If we could hear infra sound we could hear vibrations of pendulum just like how we year flattering of the wings of the bee. Infra sound producing animals

  14. Ultrasound

  15. Earthquakes produce low frequency infrasound before the main shock waves begin which alerts the animals

  16. HEARING RANGE IN DOGS The hearing ability of a dog is dependent on its breed and age. However, the range of hearing is approximately 40 Hz to 60 kHz, which is much greater than that of humans. As with humans, some dog breeds become more deaf with age, such as the German Shepherd and Miniature Poodle. When dogs hear a sound, they will move their ears towards it in order to maximise reception. In order to achieve this, the ears of a dog are controlled by at least 18 muscles. This allows the ears to tilt and rotate. Ear shape also allows for the sound to be more accurately heard.

  17. DOG’S EAR

  18. HEARING RANGE IN BATS Bats require very sensitive hearing to compensate for their lack of visual stimuli, particularly in a hunting situation, and for navigation. Their hearing range is between 20 Hz and 150 kHz. They locate their prey by means of echolocation. A bat will produce a very loud, short sound and assess the echo when it bounces back. The type of insect and how big it is can be determined by the quality of the echo and time it takes for the echo to rebound; there are two types; constant frequency (CF), and frequency modulated (FM) calls that descend in pitch.



  21. WHAT IS A HEARING AID?? A hearing aid is an electroacoustic device which typically fits in or behind the wearer's ear, and is designed to amplify and modulate sound for the wearer. Earlier devices, known as ear trumpets or ear horns, were passive funnel-like amplification cones designed to gather sound energy and direct it into the ear canal. Similar devices include the bone anchored hearing aid, and cochlear implant.

  22. H E A R I N G AID

  23. THANK YOU !!

  24. QUESTION Why are the ceilings of concert halls curved? Ceilings of concert halls are curved so that sound after reflection (from the walls) spreads uniformly in all directions. What is the audible range of the average human ear? 20 Hz to 20,000 Hz

  25. What is the range of frequencies associated with (a) Infrasound? (b) Ultrasound? (a) Infrasound has frequencies less than 20 Hz. (b) Ultrasound has frequencies more than 20,000 Hz. What is a hearing aid? What is it used for? Hearing aid is an electronic battery operated device for people with hearing loss.

  26. Give any one use of multiple reflection of sound. What is the hearing range of an elephant? Below 20 Hz