Chapter 4 Flashcards
Wave A and Wave B have the same amplitude and frequency. These two waves cross and at a given instant, Wave A is raising the pressure by 15 uPa, and Wave B is also raising the pressure by 15 uPa. What is the local pressure in uPa at that instant?
30
Two sinusoidal waves whose amplitudes and frequencies are identical are 180 out of phase. Their interference would be
Completely destructive
The drawing below shows two sinusoids of the same frequency (red solid line and dashed black line). If these two waveforms overlap in time (and space) what kind of interference will result?
2 waves in exact same phase
constructie
Peak clipping is not desirable because the sharply cut-off corners contain __ frequency components, similar to ___ waves.
high
square or rectangular
When two sinusoids of different frequencies are added together, this results in _________ .
constructive and destructive interference
The superposition principle states that, for all systems, the net response caused by two or more signals is simply the sum of the responses that would have been caused by each stimulus individually.
False - for all LINEAR systems
In a linear system, adding together two sinusoidal waveforms of the same frequency but different phases will result in the creation of a second frequency that was not present in the original waveforms.
False
Suppose that two sinusoidal waveforms are added together. The first has a frequency of 3000 Hz, and the second has a frequency of 2500 Hz. The summed waveform will show an alternating constructive and destructive interference pattern, know as “beats”. What is the beat frequency in Hz?
500
Fourier’s theorem says that any periodic waveform can be written as the sum of a series of sine and cosine waveforms.
True
Consider a waveform made up of the following sinusoidal frequencies: 200 Hz, 401 Hz, 602 Hz. This complex waveform would best be described as being
quasi-periodic
Consider a waveform made up of the following sinusoidal frequencies: 400 Hz, 800 Hz, 1200 Hz. This complex waveform would best be described as being
periodic
Consider a waveform made up of the following sinusoidal frequencies: 111 Hz, 349 Hz, 513 Hz. This complex waveform would best be described as being
aperiodic
Match each type of waveform periodicity with its correct description.
periodic:
aperiodic:
quasi-periodic:
- composed of a harmonic series; regular, repeating cycles
- contains no repeating cycles
- composed of a nearly harmonic series
A Fourier series is a harmonic series. Which of the following frequencies does NOT belong as part of the harmonic series shown below?
150 Hz, 300 Hz, 450 Hz, 500 Hz, 750 Hz, 900 Hz
500
Adding sinusoids of the same frequency (phases can be the same or different) always results in a waveform that is the same frequency (phase may vary).
True
The superposition principle states that, in linear systems, the net response caused by two or more signals is simply the sum of the responses that would have been caused by each stimulus individually.
True
Suppose that two sinusoidal waveforms are added together. The first has a frequency of 8000 Hz, and the second has a frequency of 7,937 Hz. The summed waveform will show an alternating constructive and destructive interference pattern, known as “beats”. What is the beat frequency in Hz? (You only need to enter the number for your answer. You do not need to include the unit.)
63
Suppose two acoustic waves, Wave A and Wave B, have the same amplitude and frequency. These two waves cross paths and, at a given instant, Wave A is raising the pressure by 33𝜇𝑃𝑎, and Wave B is also raising the pressure by 24𝜇𝑃𝑎. What is the local pressure in 𝜇𝑃𝑎 at that instant?
57
Consider a waveform made up of the following sinusoidal frequencies: 150 Hz, 301 Hz, 452 Hz. This complex waveform would best be described as being
quasi-periodic
Count the number of beats you hear in a second.
Now count the number of peaks in the y3 envelope in one second.
5 - they are both the same number
