Sound Waves, Sinusoids, and Spectrum Analysis in Acoustics

What type of wave does the motion of mass on a string resemble?

A sine wave

Does changing the amplitude affect the wave period or frequency?

No, changing amplitude does not change wave period or frequency.

What is the relationship between restoring force of elasticity and displacement?

The restoring force of elasticity is proportional to displacement.

What defines a pure tone?

A pure tone is a simple harmonic motion, such as a pendulum or mass-spring system sound pressure wave.

What is a waveform?

A waveform represents changes in amplitude over time.

What are the three defining characteristics of a sinusoid?

Amplitude, frequency, and phase.

How is frequency expressed?

Frequency is expressed in Hertz (Hz), which is cycles per second.

What is the fundamental frequency (fo)?

The lowest frequency of a complex periodic sound wave.

What is a complex periodic wave?

A wave that is periodic but not a simple sine wave.

What is a line spectrum in relation to complex periodic waves?

A line spectrum shows energy only at specific frequencies identified by vertical lines.

What are harmonics?

Harmonics are integer multiples of the fundamental frequency in a complex periodic sound.

What is an aperiodic sound?

A sound that does not repeat every T seconds, such as hissing or transient sounds.

What is the unit of sound pressure?

Pascal (Pa).

What does the sound pressure level (dB SPL) formula represent?

Sound pressure level is calculated as 20 log (Prms/Pref), where Prms is the RMS amplitude and Pref is the reference amplitude.

What happens when sound hits a barrier?

It can be absorbed, transmitted, or reflected.

What is reverberation?

Reverberation is the persistence of sound in a space after the original sound stops.

What is reverberation time?

The time it takes for the measured sound level to decay by 60 dB SPL.

What is the relationship between amplitude and pressure variation in sound?

Amplitude represents the amount of pressure variation about the mean.

How can you estimate peak amplitude from a waveform?

Find the distance from zero to the maximum along the y-axis.

What is the RMS amplitude of a pure tone proportional to?

It is proportional to its peak amplitude.

What is the significance of the phase spectrum?

The phase spectrum defines the starting phase as a function of frequency.

What does the amplitude spectrum of a complex periodic wave show?

It shows multiple lines corresponding to different frequency components.

What is the difference between periodic and aperiodic sounds?

Periodic sounds repeat over time, while aperiodic sounds do not.

What is the effect of atmospheric pressure on sound pressure?

Atmospheric pressure is 0 Pa, and sound pressure is measured relative to this.

What is the reference amplitude (Pref) in dB SPL calculations?

Pref is standardized at 20 micro Pascals (20 x 10^-6 Pascal).