Mr. Ganz SPH3U - Home



Sound and Sound WavesSound waves form one of our major sensory links to the world, so it is important to understand their properties. Without sound, we would be unable to communicate by speech, hear music, or know when someone has snuck up behind you. Sound waves will fall into three different categories when covering different ranges of frequencies.NameFrequency Range (Hz)CharacteristicsInfrasonic0-20Very low frequencies of sound that the human ear can’t detect, but you may feel the rumbling of the waves through your bodySonic (AKA Audio)20- 20 000Normal range for human ears, although not everyone (especially the elderly) will hear to the extremes of this rangeUltrasonic20 000 +Beyond normal hearing for humans, although some animals (like dogs) hear part ways into this range. Also used in medicine (e.g. ultrasounds)Speed of SoundThe speed of sound in air actually depends on the temperature of the air. At zero degrees the speed of sound through air has been experimentally found to be 331.4 m/s and this value increases 0.606 m/s for every increase of 1oC.v=332 ms+0.59 ms°CT [°C] where T is the temperature in oC.Remember that the speed of a wave is not only affected by the temperature but also the type of media. The same can be said about sound. Waves travel more rapidly in certain solids and in hotter gases than in cooler than cooler ones. Measuring the Speed of SoundWe are going to perform this lab as a class and we are going outside to determine the speed of sound. To perform this lab we are going to require two blocks of wood, a stopwatch, a thermometer and a meter stick. Before we begin, we need to designate one person in charge of clapping the blocks, another for measuring temperature, 3 for measuring the distance from the wall, 3 timers and two people to record all of the values.Procedure (Group)- Temperature MethodRecord the current temperature outside using the thermometer in Table A. Do this 3 times (spacing the times out when you measure)Procedure (Group)- Echo Method Have 3 students pace out what 10 meters is in the classroom. (# of steps for them) Locate a high wall with a clear space of anywhere from 50m to 100m. Have 3 students for measurements measure the distance. Take the average value of their 3 distances and use that as the distance.Now clap the blocks together and listen for the echo so that the time between the previous clap and the echo is the same as the time between the echo and the next clap. In other words, clap the blocks so that a regular rhythm is set up: clap…echo… clapWhen you have achieved the correct timing start doing the trials. Have the person in charge of the stop watch time the number of seconds required for 20 clap intervals and have somebody else record this time. Remember when counting the number of claps to start with zero.Repeat step 4 five times to get an average time. This average time interval is equal to the time taken for the sound to travel four times the distance between you and the wall. Gather all of the appropriate data from the person recording all of the values. Record in Table B. Procedure (Group)- Distance Method Have students who measure distances measure out the distance of one side of the field to the other. Have a volunteer do a dramatic clap.Have a student timer start the timer when they see the hands of the clapper go together, then stop it when they hear the sound. Do three trials, recording the results in Table C. Name:____________________Purpose:__________________________________________________________________________________________________________________________________________________________________________________________________Data Tables:Trial #TemperatureVelocity123Table A- Temperature MethodAverage Speed of Sound: ______________Trial #Distance (m)Time (s)Velocity (m/s)1234Table B- Echo MethodAverage Speed of Sound:________________Trial #DistanceTimeVelocity123Table C- Distance MethodAverage Speed of Sound:________________AnalysisUsing the average speed of sound found from the Temperature Method, how does the value of the speed of sound calculated experimentally compare to the one that you calculated from the equation (theoretical value)? What was your percentage error? (do for the Echo method and the distance method) (remember: % error=Theoretical Value-Experimental ValueTheoretical Value×100%)Account for the sources of error in this investigation and explain how they may affect the results.Knowing the speed of sound, how might you determine the distance between your point of observation and a granite cliff some distance away? ................
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