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SoundSound – a form or energy produced by rapidly vibrating objects, that can be heard by the human ear. Infrasonic – any sound that is lower than 50 HzUltrasonic – and sound that is higher than 20,000 HzFrequencies different species can hear:Human20 – 20,000 HzIn order for sound to travel it has to travel through a medium. If there is no medium, there is no sound. Space is a vacuum, it has no medium, therefore you cannot hear anything in space – it is eerily quiet. Sound travels by the compressing and rarefaction of air molecules. As the molecules compress, the pressure in the air rises. As they have rarefaction the pressure in the air decreases. Dog15 – 50,000 HzCat60 – 65,000 HzBat1,000 – 120,000 HzPorpoise150 – 150,000 HzRobin250 – 21,000 HzFrog50 – 10,000 HzMoth3,000 – 150,000 HzSound waves are represented as a longitudinal wave. But air pressure is represented as a transversal wave. Putting the two together can help us better understand the sound wave moving. 31559501410335High Air Pressure0High Air Pressure31565851958340High Air Pressure0High Air Pressure351599526733500 INCLUDEPICTURE "" \* MERGEFORMATINET 09461500 INCLUDEPICTURE "" \* MERGEFORMATINET The larger the amplitude, the louder the sound is. Pitch – is related to the frequency of a sound wave (having more waves per second). As the frequency increases, so too does the pitch and vice versa. Example – female voices are higher pitched (higher frequency) than males whom have lower pitched (lower frequency) voices. Example #1 The sound from a trumpet travels at a speed of 3.5 x 102 m/s in air. If the frequency of the note played is 3.0x102 Hz, what is the wavelength of the sound wave?v = 3.5 x 102 m/sf = 3.0 x 102 Hz = ???v = f = v/f = (3.5 x 102 m/s)/( 3.0 x 102 Hz) = 1.2 mSpeed of sound equation in different temperatures:v = 331 m/s + (0.601 m/s/C)?Twhere v = velocity in m/sT = is temperature in CExample #2Calculate the speed of sound in air when the temperature is 16C.T = 16Cv = ?v = 331 m/s + (0.601 m/s/C)?T v = 331 m/s + (0.601 m/s/C)? 16Cv = 340.616 m/sv = 341 m/sExample #3If a tuning fork puts out a tone at 440 Hz, what is its wavelength in air at 25?C? It took Karmen .05 seconds to hear the sound, how far away is she from the tuning fork? What is the wave length?T = 25Cv = ?t = .05 sf = 440 hz = v = 331 m/s + (0.601 m/s/C)?T v = 331 m/s + (0.601 m/s/C)? 25Cv = 346.025 m/sv = 346 m/sd = vtd = (346.025 m/s)(.05 s)d = 17 mv = f = v/f = 346.025 m/s/440 hz = .786420 m = .786 m. Sound Intensity – is the power of sound per unit area in watts per meter squared. Equation of sound intensity:Intensity =E/ (t x area) = P/areaWhere:E = is energy in Joulest = is time in secondsarea = is m2P = is power in WattsIntensity = is a decibel reading in db. Intensity of the sound wave decreases with increasing distance from the source.? And vice versa. The mathematical relationship between intensity and distance is:The intensity varies inversely with the square of the distance from the source. So, if the distance from the source is doubled (increased by a factor of 2), then the intensity is quartered (decreased by a factor of 4). Similarly, if the distance from the source is quadrupled, then the intensity is decreased by a factor of 16.45170274953000DistanceMathIntensity1 m-160 db2 m160/(22)40 db3 m160 /(32)17.8 db4 m160 /(42)10 dbHumans can hear the quietest of whisper 0db (10-12 W/m2), to a level that is painful to the ear 120 db (10 W/m2)Decibel – is a unit of measuring sound (db). 0 db = 10-12 W/m2, this is the threshold of hearing for humans. Decibels is a logarithmic pattern. Thus, every 10 db units change is a tenfold effect. Starting from 0 db, a sound 10 times more intense is 10 db, a sound 100 times more intense is 20 db, and a sound that is 1000 times more intense is 30 db. A sound that is painful to the ears is 130 db which is 1013 times more intense than a threshold of hearing for humans. SourceIntensityIntensity?Level# of TimesGreater Than TOHThreshold of Hearing (TOH) 10-12?W/m20 dB100Rustling Leaves 10-11?W/m210 dB101Whisper 10-10?W/m220 dB102Normal Conversation 10-6?W/m260 dB106Busy Street Traffic 10-5?W/m270 dB107Vacuum Cleaner 10-4?W/m280 dB108Large Orchestra6.3*10-3?W/m298 dB109.8Walkman at Maximum Level 10-2?W/m2100 dB1010Front Rows of Rock Concert 10-1?W/m2110 dB1011Threshold of Pain 101?W/m2130 dB1013Military Jet Takeoff 102?W/m2140 dB1014Instant Perforation of Eardrum 104?W/m2160 dB1016WorksheetNote: Use 343 m/s for sound in air if temperature is not given.What time is required for sound to travel 50.0 m through a copper pipe. The velocity of the wave is 343 m/s? What is the wavelength in meters of the sound produced by a tuning fork which has a frequency of 320 Hz? The temperature of the air is 15°C.The echo of a ship’s foghorn reflected from an iceberg is heard 5.0 seconds after the horn was blown. If the temperature of the air is – 10.0°C, how far away is the iceberg? A rifle is fired in a valley with parallel vertical walls. The echo from one wall is heard in 2.0 sec and the echo from the other wall is heard 2 sec later. What is the width of the valley?A man drops a stone into a mineshaft 250 m deep. How many seconds pass before he hears the stone strike the bottom of the shaft?What is the frequency of a tuning fork which resonates with an open tube 25.0 cm long when the temperature is 20.0 °C?A tuning fork with a frequency of 384 Hz produces resonance with a closed pipe 20.0 cm long. What is the speed of sound?On a hot summer day (35°C), a pesky little mosquito produced its warning sound near your ear. The sound is produced by the beating of its wings at a rate of about 600 wing beats per second.What is the frequency in Hertz of the sound wave?What is the speed of the sound?What is the wavelengthPlaying middle C on the piano keyboard produces a sound with a frequency of 256 Hz. Assuming we are at room temp (20°C), determine the wavelength of the sound corresponding to the note of middle C.A baseball player hit a homerun. The frequency of the sound of the bat hitting the ball is 1000 hz. The temperature is 28°C, what is the velocity of the ball. If it took 3 seconds for a fan to hear the sound, how far away are they from the batter?Determine the speed of sound on a cold winter day (T=3 degrees C).Mr. Willard is camping in the glacier parts of Banff National Park. In the midst of a glacier canyon, he makes a loud holler. He hears an echo 1.22 seconds later. The air temperature is 15 degrees C. How far away are the canyon walls?If the?temperature of the?air in?your region is?32° C, what is the speed of sound in air at that?temperature?If the speed of sound near you?is 333 m/s, what is the ambient?temperature?If the speed?of sound near?you is 350?m/s,?what is the?ambient temperature.484359987729800. A mosquito's?buzz?is often rated with a decibel rating of 40 dB. Normal conversation is often rated at 60 dB. How many times more intense is normal conversation compared to a mosquito's?buzz?a. 2b. 20c. 100d. 200e. 400The table at the right represents the decibel level for several sound sources. Use the table to make comparisons of the intensities of the following sounds. How many times more intense is the front row of a Smashin' Pumpkins concert than ... the 15th row of the same concert?the average factory?normal speech?the library after school?the sound that most humans can just barely hear?On a good night, the front row of an Our Lady Peace concert would surely result in a 120 dB sound level. Music from your cellphone produces 100 dB. How many cellphones would be needed to produce the same intensity as the front row of the Our Lady Peace concert? INCLUDEPICTURE "" \* MERGEFORMATINET ................
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