5070- Wk 2

What happens when sine waves combine?

They create complex sounds with varying frequencies and amplitudes.

How is sound intensity measured?

In decibels (dB), using a logarithmic scale.

Are pure tones common?

Nope. Everyday sounds are complex—made of many sine waves.

What’s constructive interference?

In-phase sine waves combine, doubling amplitude.

What’s destructive interference?

180° out-of-phase waves cancel out = silence.

What is the harmonic series?

Fundamental frequency + whole number multiples = periodic waveform.

What does "periodic" mean?

The waveform repeats exactly over time.

What’s "nearly periodic"?

Voice. Has a pattern, but with small irregularities.

What’s an aperiodic sound?

No pattern, no predictability—aka noise.

What happens to sound in different mediums?

It reflects off hard surfaces & transmits through continuous ones.

What boosts amplitude in reflection?

In-phase reflections (constructive interference).

What is natural resonance?

A structure’s preferred vibration frequency (like a swing’s timing).

What increases frequency?

Higher stiffness.

What decreases frequency?

More mass.

Low vs. high frequency = ? wavelength

Low = long, High = short.

What do resonators do?

Amplify preferred frequencies, dampen others.

What is damping?

Suppressing vibrations (like a piano damper or studio foam).

What are aural beats?

Result of two similar-frequency waves combining—causes pulsing sound.

Beat rate = ?

Frequency difference between the two waves.

Is 0 dB silence?

Nope. It’s the softest sound humans can just barely hear.

Can you add dB like regular numbers?

Nope. dB uses a logarithmic scale.

20 dB + 20 dB = ?

26 dB (double pressure = +6 dB).

dB SPL formula?

20 × log(measured pressure / reference pressure).

Reference pressure (for SPL)?

20 microPascals.

dB for a sound 10x louder than reference?

20 dB.

dB SPL?

Sound Pressure Level (physical pressure).

dB IL?

Intensity Level (energy over area).

dB HL?

Hearing Level (adjusted to average human hearing).

dB SL?

Sensation Level (above individual’s hearing threshold).