AP+Unit+3

Notes:

Longitudinal wave: where particles push down the length of the wave (sounds)

Transvere wave: in electronics (computor, not sound)

It's called compression (condensation) when wave forms are squished together, when pulled apart its called rarefaction

Wave length or cycle determines the pitch

Pitch is basically the highness or the lowness of any paticular sound

Wavelength is the "lambda" symbol

Waves closer, higher pitch.....waves further, lower pitch

Sound is a finite speed

Pitch is the measure of cycles per second........cycles per second measurement is frequency.....frequency is measured in hertz

Cycles are the compression of rare fraction

Hinrick Hertz....frequency named after

Double a frequency, you get the octave

Lowest sound human can hear is 20 hertz, highest is 20 kilahertz (20,000 hertz)

1,000 hertz=1 kilahertz

Loudness is a measure of amplitude

Amplitude is measured by the hight of the wave

Amplitude is measured in decibels (dB)

Decibels: logarithmic value

0 dB is virtually no sound, 120 is highest sound level (ears "bleed and blow out")

20 hertz to 20 kilahertz= range of frequencies we can hear

Timbre is what determines voice difference

Voice is different because of amount of harmonics

Timbre is amplitude of harmonics

A note contains its root, octave (root), (perfect) 5th, octave (root), 3d, 5th, flat 7th, octave (root), 9th, 3d.....harmonic series

Harmonics are overtones (other notes or tones, could be in voice) (multiply harmonic my 2, second harmonic, etc) (whole number multiple)

Pitch changes based on speed

Sine wave (no harmonics, only get electronically), square wave (odd harmonics), triangle wave (odd harmonics, amplitude of triangle wave harmonics is softer than square wave, dB level is lower than square wave), sawtooth wave (every harmonic present)



White noise every frequency at same volume, pink noise every frequency tapers off high frequencies, brown noise gets rid of highs

Complex wave form because harmonics are different (so looks different, squigle)

Sound travels at 1,100 fps at 72 degrees fahrenheit

The three components of sound are pitch, loudness, and timbre

For something to appear to be twice as loud, it has to be 10 times as loud

White noise is every single frequency, pink noise tapers off highs, brown noise has no highs

Defonitons:

Pitch
 * Period: time occupied by a single cycle
 * Wavelength: length of sound wave, determines pitch of sound
 * Cycle per second: the amount of time a waveform it completes its cycle
 * Hertz: the measure of frequency
 * Wavelength = Speed of Sound (ft/sec) / Frequency: wavelength
 * F=Speed of Sound/Wavelength: frequency

Loudness
 * Amplitude: the strength of a waveform
 * Watts: The measure of sound power/acoustic power
 * Decibels: logarithmic value of a sound, measurement unit of amplitude
 * Threshold of hearing and Pain!: 20 N/m (200 dynes/cm2) is the loudest sound we can endure

Timbre
 * Harmonic Series: The pitches which are present in a single note
 * Fundamental: The first harmonic of a note
 * Overtones: Harmonics, other notes or tones in a single note
 * Complex waveforms: Waveforms that are made up of multiple frequencies

Notes:

Graph waveform: points above zero axis correspond to points when air molcules are more dense, points below zero axis correspond to points at which the air is less dense, zero axis is the point of equillbrium, amplitude is on vertical axis

When a waveform repeats continuously, it is a periodic waveform (represented as pattern usually, pattern is a cycle)

A waveform that does not consist of a repeating single cycle is called a non-periodic waveform

Amplitude is the strength of the waveform, more specificclly it is the amount of change between the peak positive, or peak negative value and the zero axis, or to a single instantaneous amplitude at any point of the waveform It is possible that the amplitude of one waev can be greater than another, even though the duration of the cycle is the same

The amplitude of a sound contributes greatly to its perceived volume

Frequency is the rate of change in air pressure measured by the number of cycles that occur per second

Any frequency below 20 Hz is referred to as subaudio, while frequencies about 20 kHz are called ultrasonic

Frequency is a physical property of sound, while pitch is the listener's interpretation of frequency

The term phase is used to specify a particular point in time on the waveform, or to compare the relative position in time of two waveforms

Phase comparisons can express the temporal relationship between two waves

Two common ways to represent sound: analog representation or digital representation

An analog representation uses continuous and constant voltage fluctuations that change in accordance with variations in air pressure made by sound (this representation made by voltage single is called analog signal), analog signals characterized by facts that voltages representing the sound are constantly changing

Digital sampling is the process of converting of an analog representation of sound to a digital representation of sound numbers are used to represent sound)

digital sampling creates digital representation by taking measurements of instantaneous amplitudes at equally spaced intervals, each of these equally spaced measurements is a sample (sample is also used to describe digital recording in its entirety)

The rate at which measurements of the amplitude are made is the sampling rate

A sampling rate must be at least two times the highest frequency contained in the waveform to accurately represent the frequency of a waveform

The minimum sampling rate is canned the Nyquist rate, highest possible sampled frequency given a certain sampling rate is the Nyquist frequency

Aliasing is the introduction of false or alias frequencies in the digital representation that were not present in the original waveform

The term resolution refers to the number of discrete amplitudes a digital recording (or a digital synthesis system) can represent

Waveforms that are made up of multiple frequencies are called complex waveforms

When someone is synthesizing sound by combining frequencies of various amplitudes and phases is working with a process called additive synthesis

Fourier Analysis allows one to break down complex preiodic waveforms into their basic components, which are sine waves of carious frequencies, amplitudes, and phases (opposite is Fourier Synthesis)

Constructive interference is when when at some points combined waves reinforce one another to create an increased amplitude, destructive interference is when at other points combined waves interfere with one another to result in a decreased amplitude

A fundamental frequency is a frequency that has the same period as the resultant waveform, frequencies higher than the fundamental are partials

The makeup of the specific harmonics in any given waveform is called the **[|harmonic spectrum]**, or spectrum.

An overtone is any harmonic other than the fundamental

A duty cycle is the percentage of the waveform that occurs above the zero axis. This causes every other harmonic to be absent in square waves

The rectangle wave, also called a **[|pulse wave]**, may have any number of different duty cycles, but like the square wave, its harmonic spectrum is related to its duty cycle.

Clipping is where the audio recording cuts off some of the sound because it is too loud (remember audicity)....headroom space above volume that you have just recorded (if recorded at -10dB, space inbetween 0dB and -10dB)....normalize takes softest sound and moves it to 0dB....make sure that when you go to record, turn down gain (the trim) and watch meter

The amplitude of a sound wave is closely related to how it sounds....it is the "strength" of the wave

Pressure is the measure of the amount of force exerted on a particular object over a specific unit area

p=F/S where p=pressure, F=force, and s=surface area

0.00002 N/m2 (.0002 dynes/cm2) is the softest sound we can hear or the threshold of hearing or the threshold of audibility, 20 N/m (200 dynes/cm2) is the loudest sound we can endure or the threshold of pain or the threshold of feeling

Transducer converts (transduces) one form of enery (acoustical pressure) into a different form of energy (electrical voltage)

Peak amplitude (perhaps simplest type) is found by measureing the higest point above zero reached by teh wave in a given cycle......peak to peak amplitude of the wave is found by measuring the difference between the highest and lowest points in a given cycle, which will be equal to twice the peak amplitude for any periodic wave

Root-mean-square (rms) is the most effective way to measure sound waves in way that closely correlates amplitude with loudness or power, calculated by taking large number samples of the sound waves at regular intervals, squaring the samples to remove negative values, adding up all the squared values, dividing the sum by the total number of samples, and taking the square root of the result

Rms is a very precise type of average that correlates closely to the power inherent in a sound wave and therefore to apparent loudness

For continuous sine waves, rms amplitude is more easily calculated from peak amplitude

N=Newtons, metric unit for force

Meters in the recording studio can either display average or peak level (or both)

Questions:

1. The vibration of an object causes variations in ?? which are transmitted through the air in sound waves. Air pressure

2. As the sound wave travels through the air the air molecules experience (being pushed together), and (pulling apart). Pushed together is called:?? compression Molecules pulled apart is called:?? rarefaction

3.. The frequency range of human hearing is from ? 20 Hz to ? 20 kHz

4. The perceived intensity or volume of a sound is measured in units called ?? decibels

5. The intensity level known as the “threshold of pain” is ?? 20n/m squared

6. List three waveforms commonly used as building blocks for synthesis:

a. Sine waves

b. Triangle waves

c. Sawtooth waves

7. The frequency of a pitch one octave higher than 450 Hz is 900 Hz.

8. To double the loudness of a sound, the power must increase ?? 10 times.

9 . The amount of energy expended in making a sound is called the power of the sound and is measured in hertz??

10. The predominant perceived pitch of a timbre is called the root??

11. The series of frequencies present in a timbre is called the ?? harmonic series.

12. “Cycles per second” or “cps” measures what aspect of sound? Pitch

13. Amplitude is a measurement of a sound's loudness??

14. Timbre or tone color is created by the many different harmonics present in a sound.

15. Describe the Doppler Effect. The Doppler Effect is the change in frequency of a wave for an observer moving relative to the source of the wave.

=**Playing with Waves:** Provide answers to the questions below in your wiki. =

Download the following Sample. [|Wave 1.wav] Load sample into Audacity
 * First Example:**

Using the magnifying glass, zoom in and identify the shape of the wave.

//Sine wave//

Highlight the waveform and then go to the effects menu.

Select Change Pitch. Raise the pitch and note the change in the shape of the wave form.

//I raised the pitch from F to C and the distance between each wave became smaller, so the frequency of the waves increased.//

Select Amplify - click allow clipping - then raise the amplitude by 5 dB. What happens to the wave shape?

//The waves are cut off or clipped because the decibel level is to high.//

Undo (Apple Z)

Select a small section of the wave form, after zooming in, and select invert from the effects menu. What happens to the wave form?

What happens to the wave when you lower the pitch under the effects drop down menu?

[|Wave 2.wav]
 * Second Example:**

Zoom in and identify the wave shape.

Does this wave sound different than the first? If so How?

[|Wave 3.wav]
 * Third Example:**

Zoom in and identify the wave shape.

Describe the sound quality of this wave.

Why do the three waveforms sound different?

[|Wave 4.wav]
 * Fourth Example:**

Can you explain why the shape of this wave is the way it is?

Using the Effects Menu, fade the sound clip in at the beginning and fade it out at the end. How is the wave shape altered?

With that wave still open, select analyze from the dropdown menu.

What information is provided on this graph?

What observations can you make about the sound analysis?