# MTD2 class 3

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## Review Sound Properties

There is a good reading and a bunch of supplemental readings in the High School Physics Tutorial

1. Which wave (Wave1 or Wave2) has a Lower Frequency?
2. Which wave (Wave1 or Wave2) has a Higher Amplitude?
3. Which wave (Wave1 or Wave2) has a Longer Wavelength?
4. Which wave (Wave1 or Wave2) has a Faster Speed?
5. Which wave (Wave1 or Wave2) has a Higher Pitch?
6. Which wave (Wave1 or Wave2) is Louder?

## The Ear and Hearing Loss

Outer Ear

• Pinna
• Auditory Canal
• Ear Drum

Inner Ear

• Mallus, Incus, Stapes
• Semi-Circular Canals
• Cochlea
• Eustachian Tube
• Auditory Canal

Hearing Loss

## Perception of Amplitude and Frequency

Humans do not hear all frequencies equally. We perceive different frequencies with equal energy to have different amplitudes. The Fletcher Munson Curves show the phons scale, how amplitude is perceived by frequency

Fletcher Munson Curves 1 http://arts.ucsc.edu/EMS/Music/tech_background/TE-02/AcNumbers/AcNumbers.html

Fletcher Munson Curves 2 http://www.allchurchsound.com/ACS/edart/fmelc.html

Fletcher Munson Curves 3 http://hyperphysics.phy-astr.gsu.edu/hbase/sound/eqloud.html

## Behaviour of sound waves

• Interference and Beats
• The Doppler Effect and Shock Waves
• Boundary Behavior
• Reflection, Refraction, and Diffraction

## Envelope

Envelope is the Time/Amplitude shape of the wave. It is essentially a means of amplitude thought time.

Robert L Mott's Nine Components of Sound

Attack -- Decay-- Sustain -- Release

## Different Domains of sound

### Time Domain

Time along X axis and Amplitude Y axis -Fixed 2/29/00

Sine wave looks like a sine wave

### Frequency Domain

Freq. along X axis and Amplitude Along Y axis-Fixed 2/29/00

Sine wave looks like a line

## RMS

root mean square Abbr. rms, RMS Mathematics. The square root of the average of the squares of a group of numbers. A useful and more meaningful way of averaging a group of numbers.

The RMS averaging method is a better method for determining the amplitude of sound. Dynamic Range Definition @http://www.rane.com/par-d.html

The dynamic range of an audio system or and audio performance is the difference between the peak noise level and the noise floor.

## Dynamic Range

Dynamic range = (Peak Level - Noise Floor)

Definition @http://www.rane.com/par-h.html

The head room of an audio system is is the difference between the nominal level and the Peak level (or clipping point) Frequency Response Definition @http://www.rane.com/par-f.html

The range in frequency that an audio system or program contains or can pass between certain deviation.

Do the top one

## Quiz 1 review

Properties of sound High school physics tutorial

```   * Sound Is a Longitudinal wave
* Speed of sound (measured in m/s)
* Frequency (measured in Hz)
* Period (seconds per cycle)
* Wavelength (measured in meters)
* Amplitude/Pressure (for this class we will only look at dBs)
* Phase (measured in degrees)
```

Understand the difference between transverse and longitudinal waves.

Be able to calculate frequency from wavelength or period and visa-versa.

Understand

```   * dB's
* Different ways of representing and audio wave (the Domains of Sound)
* Timbre/Harmonic structure