INTONATION

In linguistics, intonation is variation of pitch while speaking which is not used to distinguish words. It contrasts with tone, in which pitch variation doesdistinguish words. Intonation, rhythm, and stress are the three main elements of linguistic prosody. Intonation patterns in some languages, such as Swedish and Swiss German, can lead to conspicuous fluctuations in pitch, giving speech a sing-song quality. Fluctuations in pitch either involve a rising pitch or a falling pitch. Intonation is found in every language and even in tonal languages, but the realisation and function are seemingly different. It is used in non-tonal languages to add attitudes to words (attitudinal function) and to differentiate between wh-questions, yes-no questions, declarative statements, commands, requests, etc. Intonation can also be used for discourse analysis where new information is realised by means of intonation. It can also be used for emphatic/contrastive purposes.

All languages use pitch pragmatically as intonation — for instance for emphasis, to convey surprise or irony, or to pose a question. Tonal languages such as Chinese and Hausa use pitch for distinguishing words in addition to providing intonation.

Generally speaking, the following intonations are distinguished:

• Rising Intonation means the pitch of the voice rises over time [↗];
• Falling Intonation means that the pitch falls with time [↘];
• Dipping Intonation falls and then rises [↘↗];
• Peaking Intonation rises and then falls [↗↘].

Intonation contours in English

Not all rises and falls in pitch that occur in the course of an English phrase can be attributed to stress. The same set of segments and word stresses can occur with a number of pitch patterns.Consider the difference between:

• You're going. (statement)
• You're going? (question)

The rise and fall of pitch throughout is called its intonation contour.English has a number of intonation patterns which add conventionalized meanings to the utterance: question, statement, surprise, disbelief, sarcasm, teasing.An important feature of English intonation is the use of an intonational accent (and extra stress) to mark the focus of a sentence. Normally this focus accent goes on the last major word of the sentence, but it can come earlier in order to emphasize one of the earlier words or to contrast it with something else.

People have a tendency to think of intonation as being directly linked to the speaker's emotions. In fact, the meaning of intonation contours is as conventionalized as any other aspect of language. Different languages can use different conventions, giving rise to the potential for cross-cultural misunderstandings.Two examples of cross-linguistic differences in intonation patterns:

Contrastive Emphasis

Many languages mark contrastive emphasis like English, using an intonational accent and additional stress.Many other languages use only syntactic devices for contrastive emphasis, for example, moving the emphasized phrase to the beginning of the sentence.

• Instead of
  • I want a car for my birthday. (as opposed to a bike)
• you would have to say something like:
  • A car I want for my birthday.
  • It's a car that I want for my birthday.

Listeners who speak the second type of language will not necessarily interpret extra pitch and volume as marking emphasis. Listeners who don't speak the second type of language will not necessarily interpret a different word order as marking emphasis (as opposed to assuming that the speaker doesn't know basic grammar).
The normal intonation contours for questions in English use:

• final rising pitch for a Yes/No question
  • Are you coming today?
• final falling pitch for a Wh-question
  • When are you coming? Where are you going?

Using a different pattern typically adds something extra to the question. E.g., falling intonation on a Yes/No question can be interpreted as abruptness. Rising intonation on a Wh-question can imply surprise or that you didn't hear the answer the first time and are asking to have it repeated.These patterns too can be different across languages. 

COMBINING WAVES

Sound is caused by small areas of high and low pressure progragating outward from the source.
One convenient way to diagram a sound wave is to graph the pressure at each point in time, the way it might be picked up by a microphone for example:

This simplest kind of pressure wave is called a sine wave. Interesting things to measure for a sine wave:

1. amplitude (or loudness, size of pressure differences)
   usually measured in decibels (dB)
2. wavelength
3. frequency (or pitch)
   usually measured in cycles per second, or Hertz (Hz)

Frequency and amplitude are independent of each other. Two sine waves may have the same frequency and different amplitudes, and vice versa.
Wavelength is the converse of frequency: the shorter the wavelength, the higher the frequency; the longer the wavelength, the lower the frequency. (Sound will move at the same speed, about 330 metres per second. So if you want to double the frequency of a wave, you'll have to fit twice as many wavelengths into that 330 metres, and each wavelength will have to half as long.)

Combining waves

If you're listening to waves from two sources at the same time:

• a high pressure from one will cancel out a low pressure from the other
• two high pressures will reinforce each other
• two low pressures will reinforce each other

You can get the overall effect by adding the waves' pressures together at each point in time. (You have to treat the normal air pressure as zero, so that a higher pressure is positive and a lower pressure is negative.) 
The two red waves added together produce the blue wave. At the first green line, both red waves have high pressure and reinforce each other to give an extra high pressure in the blue wave. At the second green line, the two red waves have opposite pressures and cancel each other out.
The following two sounds have frequencies of 300 Hz and 500 Hz:
 300 Hz 

 500 Hz

They can be added together:

to produce a complex wave:
 
This is important because:
Any complex wave can be treated as a combination of simple sine waves.
We usually don't care about the actual complex wave itself. We're only interested in the frequencies and amplitudes of the simple waves that it's made up of. Two more examples:
 300 Hz and 2000 Hz added
 900 Hz and 1100 Hz

Comparison with light

We see simple light waves (with only one frequency) as one of the colours of the rainbow. Combining together two or more simple one-frequency sine waves produces more complex colours. The more frequencies you add, the whiter the colour gets. With light, you can easily separate the frequencies by shining the complex light wave through a prism.

The set of frequencies in light wave (as separated by a prism) is called its spectrum.

Scientists can identify different substances by looking at the spectrum of the light the substances emit when they're heated. Iron will glow with a different set of frequencies than nickel or sulphur.The situation is similar with sound. The complex wave for an [i] will be composed of a different set of frequencies than the complex wave for [a].We need a way to separate a complex sound wave out into its component frequencies (and their amplitudes) so that we can see what makes vowels different. A spectrograph is essentially just a prism for sound.