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a afreen

on 16 January 2013

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MULTIPLE REFLECTIONS GROUP 1 GROUP MEMBERS Acoustic Soundboard MEGAPHONES REFLECTION OF SOUND WHY DO AUDITORIUMS HAVE CURVED SURFACES???? When Sound is incident on a solid or a liquid surface it bounces off the surface like light rays. Sound waves also obey the laws of reflection and refraction A megaphone, is a portable, usually hand-held, cone-shaped acoustic horn used to amplify a person’s voice or other sounds and direct it in a given direction. The sound is introduced into the narrow end of the megaphone, by holding it up to the face and speaking into it, and the sound waves radiate out the wide end. The megaphone increases the volume of sound by increasing the acoustic impedance seen by the vocal cords, matching the impedance of the vocal cords to the air, so that more sound power is radiated. It also serves to direct the sound waves in the direction the horn is pointing. It somewhat distorts the sound of the voice because the frequency response of the megaphone is greater at higher sound frequencies. Since the 1970s the voice-powered acoustic megaphone has been replaced by the electric megaphone, which uses electric power to amplify the voice. Acoustic soundboard. They come in all shapes and sizes, there are variations known as acoustic backboards, which are panels placed behind the performer with a panel above that angles forward. The purpose of a soundboard is to rebound the sound from the ceiling to the audience during a concert so they can hear it and not multiple echoes due to reflection of sound. The one we see here is most likely for either a choir or a soloist, as high pitches travel upwards, so acoustic soundboards help direct the sound, projecting it into the audience. This one is cabled, which means it can be lowered or raised. Some are just fixed to the ceiling. In orchestras, acoustic backboards are used to project the brass and winds in the back which are otherwise drowned in all the strings. The soundboard is used to project smaller numbers of performers. THANK YOU A stethoscope is a diagnostic instrument used by various health care professionals to listen to or auscultate a patient’s heart, lungs, various pulse points and abdomen.The stethoscope gathers sound and sends it to the ear of the listener. It does this through the two parts of the chest piece: the diaphragm and the bell. The bell looks just as you would imagine, a tiny hollow bell with the clapper removed. If you have ever tried listening to a tin cup '"telephone" in which two tin cans are connected with a taut string, this is how the bell portion of the stethoscope works. When the bell is placed against the skin, acoustic pressure waves travel directly up the hollow tubes and into the ear. Your ear translates these vibrations into sound. The bell is most useful in picking up low frequency sounds.The diaphragm picks up higher frequency sounds. The diaphragm has a hard disc of plastic inside, and when the doctor rests it against your heart, lungs or abdomen, your body's sounds vibrate the hard plastic disc and acoustic pressure waves are created. These waves travel up the hollow tubes to the listener's ears. Multiple reflection of sound is the process in which sound waves bounces off obstacles and reflects many times before reaching the destination. STETHOSCOPE When sound reflects off a special curved surface called a parabola, it will bounce out in a straight line no matter where it originally hits.
Many stages are designed as parabolas so the sound will go directly into the audience, instead of bouncing around on stage.
If the parabola is closed off by another curved surface, it is called an ellipse.
Sound will travel from one focus to the other, no matter where it strikes the wall.
A whispering gallery is designed as an ellipse.
If person 'A' stands at one focus and person 'B' stand at the other, A's whisper will be heard clearly by 'B'.
No one in the rest of the room will hear anything. AFREEN
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