Speed of Sound - LAZSTA - home声音的速度lazsta回家.doc

Speed of SoundThe following apparatus was used to collect data used to calculate the speed of sound in air.Describe the investigation carried out using this equipment. You must use the words: sensor, data logger, reflection, echo, pulse. Underline these words in your description. The length of the pipe was 2 m (not 1 m as shown in the diagram)This graph shows the results obtained by the data logger. Use this data to calculate the speed of sound. Analysis - solutionsDescription of the investigation:A microphone sensor was attached to a data logger. The microphone was placed level with the open end of a 2 m length of 90 mm diameter PVC pipe. The opposite end of the pipe was sealed with a glass Petri dish taped into the end. The data logger was set up using the “trigger mode” so that it would start automatically when a sound was detected and to collect data for 0.025 seconds. A short sharp sound, a pulse, was produced by clapping hands once near the microphone. The sound travelled through the air in the tube to the glass barrier at the other end. The sound energy was reflected back to the microphone, which detected this echo.Results - graphAnalysisWhen a sound wave pulse is reflected from a solid barrier there is a phase reversal of the pulse. This phenomenon is clearly visible in the case of a transverse pulse in a spring as shown in the following diagram. A pulse approaching a barrier at the right-hand end on the lower side of the spring is reflected from the barrier so that it returns on the upper side of the spring.If the graph from the data logger is examined carefully, it can be seen that despite its complexity, there are negative peaks on the echo corresponding to positive ones on the original pulse one such pair has been identified using a square surrounding each point on the graph. The time interval between these identified points is the time that it takes the sound pulse to travel to the end of the pipe and back again four metres.The time interval is thus calculated:Dt = 0.0129 0.0013 = 0.0116Thus the speed, v of the sound in air is calculated as follows:v = r/Dt = 4/0.0116 = 345 ms1DiscussionSound velocity in a gas depends on both the type of gas and the temperature of the gas. In air the velocity of sound increases at the rate of 0.59 ms-1C-1 from the value of the speed of sound, 331.45 ms1, at STP (0C and 1 atmosphere pressure).i.e. the speed of sound at temperature T is:vT = 331.45 + 0.59TT is in degrees CelsiusProblem: Calculate the speed of sound at a temperature of 25C. (The answer, calculated by substitution into the above equation, is 346 ms1)This figure is in excellent agreement with the value calculated from the experimental data in this investigation.ConclusionThe speed of sound in air was calculated from data collected with an electronic data logger to be 345 ms1. This value is varies by less than 1% from the value calculated using the temperature corrected equation for the speed of sound in air that has been established by physicists. Agreement with accepted values, based on a single experiment, should be treated with cau