In this lab i will be attempting these questions on wave-forms which will help me learn how to calculate the speed, wave length and frequency of sound.
Q1: In a recording room an acoustic wave was measured to have a frequency of 1KHz. What would its wavelength in cm be?
Answer:
Formula: v = f * λ
the sound in which the sound travels through the air is roughly 333m/s and we are told the frequency is 1kHz or 1000 Hz
therefore we can use the equation above to get the answer
λ = v / f
λ = 333 / 1000
λ = 0.333
there are 100 cm in a meter so we use this to convert our answer
0.333 * 100
= 33.3 cm.
Q2: If a violinist is tuning to concert pitch in the usual manner to a tuning fork what is the likely wavelength of the sound from the violinist if she is playing an A note along with sound from the pitch fork
Answer:
the frequency of a A note on a violin is 440Hz as is a standard A tuning fork
the wavelength is
λ = v /f
λ = 333 / 440
λ = 0.756818181818181818181818.....
λ = 0.76 ~(2 Decimal Places)
because the two frequency's are the same the to wave peaks will add together and the two troughs subtract from each other to give 880Hz and the wavelength of
λ = v /f
λ = 333 / 880
λ = 0.378409090909090....
λ = 0.38 (2 Decimal Places)
Q3: If an acoustic wave is traveling along a work bench has a wavelength of 3.33m what will its frequency be? Why do you suppose that is it easier for this type if wave to be travel through solid materials?
Answer:
for the arguments sake lets assuming the work bench is made of hard wood, the the speed in which the sound will travel through it will be approximately 3600 m/s
now that we know the speed and the wavelength we can work out the frequency
f = v / λ
f = 3600 / 3.33
f = 1081.081081....
f = 1081 (2 Decimal Places)
it is easier for this type of wave to pass through solid materials because the particles are closer togther meaning that as soon as the wave hits one particle it is more or less touching the next particle due to the particles being so close together where as when the waves travel through the air the particles are more spaced out so it would take long for the waves to reach each particle.
Q4: Sketch a sine wave accurately of amplitude 10, frequency 20Hz. Your sketch should show two complete cycles of wave. What is the duration of one cycle? What is the relationship between the frequency and the duration of one cycle?
f = 20Hz
t = 1 / f
t = 1 / 20
t = 0.05
Q5: The topic “Standing Waves”. Write a detailed note
explaining the term and give an example of this that occurs in real life.
(Where possible draw diagrams and describe what represent)
Standing waves (or stationary waves) are made up as a result of the superposition of two waves with matching amplitude and frequency, which travel at the same speed, but in opposite directions of each other.
Q6: What is meant by terms constructive and destructive interference?
A constructive interference is when to waves have the same displacement they add together and make a bigger displacement. A Destructive interference is when to waves with different displacements add together which causes them to cancel each other out .
Q7: What aspect of an acoustic wave determines its loudness?
The loudness is measured in decibels (db)
Q8: Why are decibels
used in the measurement of relative loudness of acoustics waves?
decibels are used to measure the loudness and intensity
Q9: How long does it take a short 1KHz pulse of sound to travel 20m verses a 10Hz pulse?
t = v / d
t = 340 / 20
t = 17
there fore the time it will take is 17 seconds
Q10: Does sound travel under water? If so what effect does the water have?
Answer:
Conclusion
At the end of this lab i have learned about how to calculate the speed, wave length and frequency of sound, how to measure in decibels and how fast speed travels through different materials and surfaces. next week i will be doing the lab: Audio Signal Processing – Generating Signals with GoldWave.
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