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Intermediate 1 Physics Sound and Music Sound Waves Speed of Sound Using Sound Amplified Sound Beath High School - Int 1 Physics 1 Intermediate 1 Physics Sound and Music Sound Waves Beath High School - Int 1 Physics 2 Sound Waves Vibrations Musical instruments produce sound when part of the instrument vibrates. v _ _ _ _ _ _ _ A guitar string vibrates when it is plucked. Beath High School - Int 1 Physics 3 Vibrations A trumpet blasts out sound when the aair_ _ inside it vibrates Energy is transferred from the vibrating object to the listener by sound wwaves _ _ _ _ which travel through the air. These sound waves make the air vvibrate. _ _ _ _ _ _. Beath High School - Int 1 Physics 4 Frequency Each note or sound has a frequency which is measured in h _hertz _ _ _ (Hz). A tuning f fork _ _ _ has the frequency engraved on it. This vibrating fork will produce 256 vibrations every s _second. _ _ _ _. This means that 256 sound w _waves _ _ _ are produced in one second. Beath High School - Int 1 Physics 5 Frequency F _ Frequency _ _ _ _ _ _ _ = number of waves produced in one second. Beath High School - Int 1 Physics 6 Frequency A whistle produces a hhigher _ _ _ _ _ frequency sound than a vibrating drum. The whistle has a much higher pitch p _ _ _ _. The higher the pitch means the higher the frequency f _ _ _ _ _ _ _ _ Beath High School - Int 1 Physics 7 Detecting Sound S _ _Sound _ _ can be taken in by a microphone and a trace displayed on an oscilloscope. tuning fork microphone Oscilloscope sound w aves travel from fork to microphone Beath High School - Int 1 Physics 8 Loud and quiet A loud sound transfers more e _energy _ _ _ _ so the oscilloscope trace will have a llarge _ _ _ _ amplitude. The amplitude of a wave is the distance from the m _ middle _ _ _ _ of the wave to the top or bottom of the wave. Beath High School - Int 1 Physics 9 Loud and quiet Loud note has large amplitude Beath High School - Int 1 Physics 10 Loud and quiet A soft/quiet sound transfers less l _ _ _ energy so the oscilloscope trace will have a s _ small _ _ _ amplitude Quiet note has small amplitude Beath High School - Int 1 Physics 11 High and Low Frequency The effect of changing the frequency of a note can be seen on the oscilloscope screen. Sound A has low frequency Sound sound Sound B has high frequency B_ has a higher frequency than _ A . Beath High School - Int 1 Physics 12 High and Low Frequency If the frequency is doubled, we say that sound B is an o _ octave _ _ _ _ higher than sound A. frequency: (Hz) 256 512 1024 one octave t _two _ octaves Beath High School - Int 1 Physics 13 Changing the Note A musician tunes a guitar by making the string t _ tighter _ _ _ _ _ or looser. While playing the guitar, the note is changed by altering the llength _ _ _ _ _ of string which vibrates. Beath High School - Int 1 Physics 14 Changing the Note S _Short _ _ _ strings produce a higher frequency than long strings. T _Tight _ _ _ strings produce a higher frequency than slack strings. Beath High School - Int 1 Physics 15 Changing the Note An organ produces a variety of musical notes which depend on the llength _ _ _ _ _ of the air column which vibrates. The shorter pipes have the shorter air columns which produce the hhigher _ _ _ _ _ frequency notes. Beath High School - Int 1 Physics 16 Intermediate 1 Physics Sound and Music Speed of Sound Beath High School - Int 1 Physics 17 Speed of Sound During a thunderstorm, the lightning flash is seen a short time b _between _ _ _ _ the roll of thunder is heard. This is due to the fact that l _light _ _ _ travels much faster than sound through the air. In air: Speed of light = 300 000 000 m/s Speed of sound = 340 m/s Beath High School - Int 1 Physics 18 Calculating the Speed of Sound In a laboratory the speed of sound can be calculated using the formula below. distance speed = time (meaning; speed equals distance d _ _ _ divided _ _ _ by time) Beath High School - Int 1 Physics 19 Speed of Sound : Apparatus electronic timer Hammer different microphone A Beath High School - Int 1 Physics microphone B 20 Speed of Sound A loud sound is made. As the sound reaches microphone A, the timer starts s _ _ _ _ _. When the sound waves reach microphone B, the timer s _stops _ _ _ . The distance between the microphones is measured with a m _ _ _ _ stick. metre The experiment can be rrepeated _ _ _ _ _ _ _ to calculate a more accurate, average result. Beath High School - Int 1 Physics 21 Speed of Sound Example: Recorded times: 0.0030 s, 0.0029 s, 0.0031 s, 0.0027 s, 0.0029 s Average time = 0.0146/5 = 0.0029 s Distance travelled = 1 metre Speed = distance/time = 1.0/0.0029 = 344.8 m/s Beath High School - Int 1 Physics 22 Intermediate 1 Physics Sound and Music Using Sound Beath High School - Int 1 Physics 23 Using Sound Sound can travel through ssolids, _ _ _ _ _, liquids and gases. g _ _ _ _. The only thing that sound cannot pass through is a vacuum. v _ _ _ _ _. A vacuum is an e _empty _ _ _ space, so there are no particles to pass on the vibrations. Beath High School - Int 1 Physics 24 Using Sound When listening to music, you hear s _sounds _ _ _ _ with a wide range of frequencies. We can detect sounds that range from about 20 hertz to 20 000 hertz. As we get oolder _ _ _ _, the upper limit gradually falls to about 15 000 hertz. Some animals can detect higher frequency sounds than humans. h _ _ _ _ _. Beath High School - Int 1 Physics 25 Using Sound - Ultrasound Sound beyond the u _upper _ _ _ limit of human hearing (20 000 Hz) is called ultrasound. Ultrasound can be used in hospitals to scan the b baby _ _ _ in the mother's womb. This can be used by a computer to produce an i _image _ _ _ of the baby on a screen. Beath High School - Int 1 Physics 26 Using Sound - Ultrasound A system called s _sonar _ _ _ is used by fisherman at sea. The ultrasound signal is transmitted towards the sea bed and an e echo _ _ _ is detected. Shoals of f _ _ _ are located by fish this method. Beath High School - Int 1 Physics 27 Sound Levels The sound level of a noise means how l_loud _ _ it is. The sound level varies depending on the source of the sound. Sound level is measured in d _ _decibels _ _ _ _ _ (dB). Beath High School - Int 1 Physics 28 Sound Levels 130 J Jet _ _ engine at 50 metres 100 Pneumatic drill d _ _ _ _ Sound l level ____ (dB) 70 Rush hour ttraffic _ _ _ _ _ _ 0 S _ _ _ _ _ _ Silence Beath High School - Int 1 Physics 29 Sound Levels When sound levels rise to unacceptable levels, the problem is described as n _noise _ _ _ pollution. There are many sources of noise pollution, such as aircraft noise or pneumatic drills. Exposure to high sound levels over a long time can ddamage _ _ _ _ _ our hearing. Listening through stereo headphones will produce a harmful effect if the v _ volume _ _ _ _ is turned to maximum. Beath High School - Int 1 Physics 30 Intermediate 1 Physics Sound and Music Amplified Sound Beath High School - Int 1 Physics 31 Amplified Sound A stereo system can be used to l _ listen _ _ _ _ to a compact disc (CD) or a radio programme. No matter what function is selected, the signal passes through an amplifier which turns a small amplitude electrical s _ signal _ _ _ _ into a higher amplitude one. Beath High School - Int 1 Physics 32 Amplified Sound Amplifier large amplitude output signal small amplitude input signal Only the amplitude of the signal is changed. The frequency does n not _ _ change. When announcements are made at airports and stations, the message has to be changed from sound into e _ _ _electrical _ _ _ _ _ _ signals and back to sound. Beath High School - Int 1 Physics 33 Amplified Sound When announcements are made at airports and stations, the message has to be changed from sound into e _ _ _electrical _ _ _ _ _ _ signals and back to sound. An electronic system of 3 parts is used to amplify the s _ _ _ _ given out by the announcer signal sound Input microphone Process amplifier Output loudspeaker Beath High School - Int 1 Physics sound w ith increased amplitude 34 Amplified Sound Part of the system Function m _ _ microphone _ _ _ _ _ _ _ converts sound into an e _ _ _electrical _ _ _ _ _ _ signal a _ _ _amplifier _ _ _ _ _ makes the electrical signal sstronger _ _ _ _ _ _ _ (bigger amplitude) converts the electrical l _ _ _loudspeaker _ _ _ _ _ _ _ signal back to ssound _ _ _ _ Beath High School - Int 1 Physics 35 Voltage Gain The performances of different amplifiers can be compared by finding the gain of the amplifier. Voltage gain = 0utput voltage Input voltage Beath High School - Int 1 Physics 36 Voltage Gain Example: Find the voltage gain of the following amplifier. input 0.01V Beath High School - Int 1 Physics output 4V 37 Voltage Gain Voltage gain = 0utput voltage Input voltage = 4 0.01 = 400 N.B. Voltage gain is just a number. It has no unit u _ _ _. Beath High School - Int 1 Physics 38 Playback A recording of your own v _voice _ _ _ will sound a bit strange when it is played back from a cassette. This is because we normally hear our own voice by: vibrations of bones in our s _skull _ _ _ and ears vibrations in the air being detected by our e _ _ _ When we listen to a recording of our own voice we hear it by: vibrations in the aair_ _ being detected by our ears only. Beath High School - Int 1 Physics 39 Playback A CD (compact disc) is a source of high h _ _ _ quality sound. As the CD spins inside the CD player, light from a l _laser _ _ _ reflects off the CD. There is no wear and tear of the disc surface and there is very little background noise. n _ _ _ _. Beath High School - Int 1 Physics 40 Intermediate 1 Physics Sound and Music End of Unit Beath High School - Int 1 Physics 41