4 Characteristics of Sound Waves Audible Range: Range of sound the average human can hear.Low Frequency: 20 HzHigh Frequency: 20,000 Hz
5 What is the range of sound called that falls below the frequency of 20 Hz? non-sonicinfrasonicunsonicAntisonic
6 Infrasonic is the term used for a sound wave that falls below the 20Hz frequency. Humpback whales communicate on infrasonic frequencies.The term that describes sound waves above the 20,000 Hz frequency is called ultrasonic.Dogs can hear ultrasonic frequencies. This is why a good dog whistle cannot be heard by humans.
7 If the speed of sound is 343 m/s, what is the wavelength of an ultrasonic wave with a frequency of 35,000 Hz?.00980.01
8 Frequency determines the pitch of the sound Frequency determines the pitch of the sound. Whether the sound is a high or low pitch.Ultrasonic waves produce ultrasonic images.
9 Speed of Sound Depends on Medium Sound travels fastest through medium which are more dense. Why?Sound is the vibration of particles in a substance. The closer the particles, the faster the transfer of energy.Iron: 5130 m/s Water: 1490 m/sAir: 331 0° C
10 Why would the temperature of air effect the speed of sound in air? because hot air rises.because the temperature adds energy to the wave.because the particles in the air move faster.
11 In Fact…..The speed of sound in air increases by .6 m/s every °C the air temperature goes up.So at room temperature, 20 °C, the speed of sound in that room is m/s.
12 The temperature on a hot sunny day is around 30° C, what is the speed of sound in m/s? 3490.1
13 Sound waves propagate in 3 dimensions. Spherical wave fronts that are large distances away from the source appear to be plane waves.
14 The Doppler EffectRelative motion creates an Apparent change in frequency.
15 The Doppler EquationVdetector: Positive if listener is moving toward sourceVdetector: Negative if listener is moving away from sourceVsource: Negative if source is moving toward listenerVsource: Positive if source is moving away from listener
16 A siren produces a frequency of 1500Hz A siren produces a frequency of 1500Hz. A runner who is passing the siren at 25 m/s hears the siren. What frequency is heard when the runner is going toward the siren? (Use 343 m/s for Vsound)1390 Hz1398 Hz1617 Hz1609 Hz
17 Loudness (Sound Intensity) The intensity or loudness of a sound is perceived by a person’s sense of hearing.Each person perceives sound differently.The intensity scale numerically determines the “strength” of the sound.
24 DecibelsAs stated earlier, decibels measure the relative loudness of sound.For every 10 dB, the sound is 2 times as loud.Therefore the difference between 0 dB and 120 dB is 4096 x louder.
25 DecibelIf we have an object that is 20 dB and want to make a 50 dB sound, how many more objects do we need?Rule: for every 10 dB added, we increase the # of objects by a power of 10.
26 DecibelSo for our last example we went from 20 dB to 50 dB which is a difference of 30 dB.30 dB is 3 sets of 10Therefore for every set of 10 we increase by a power of 101 = 20 dB, then 1000 = 50dB
27 Decibel What is we want to double the number of objects? Rule: if the number of objects are doubled, then the dB increase by 3.Example: if there are 200 goats that make 70 dB, then 400 goats make 73 dB.
28 IF one horn produces 50 dB how much louder is it if it produces 80 dB? 2468
29 If there are 30 ants making a noise of 20 dB, how many ants would make a 60dB noise? 300000300003000300
30 40 bells make 70 dB. How many Bells are needed to make 96 dB? 160000.0