Sound_Concept_2

Subject Facts

Volume

Loudness, volume and amplitude are different terms for the same basic concept, Amplitude is a measure of the vertical distance between the 'peak' and the trough' of a sound wave as represented on an oscilloscope. The louder the sound, the more powerful the sound pulse: the sound wave (or pressure wave) of an explosion can sometimes cause as much damage as the flying debris, In general the harder you hit a drum the greater the vibrations are and the louder the sound.

Loudness is measured in decibels (dB). This is a non-linear measure: an increase of 10dB means that the sound is 10 times as loud. A sound level of 0dB is near to absdute silence (30dB is a quiet whisper). 140dB is the level at which permanent hearing damage can be caused. The pressure of the sound waves at 140dB is 10,000,000 times greater than at 0dB.

Pitch

Stronger vibrations are not to be confused with faster vibrations, The faster an object vibrates, the higher the pitch of the note It produces — that is, the more frequent the sound pressure pulses are. Musical notes correspond to particular frequencies of vibration. For example, middle C is 256 vibrations per second, or hertz (Hz). An octave higher is 512Hz; an octave lower is 128Hz. In general other things being equal a smaller, thinner or tighter vibrating object will have a higher pitch. Some instruments can be 'tuned' to a particular pitch or frequency (for example, by tightening a guitar string).

A glass bottle partly filed with water can be made to produce a note in two distinct ways: hitting and blowing. If you strike it with a beater; you will notice that the key factor in determining the pitch of the sound is the amount of water: more water makes a lower note. If you blow across the mouth of the bottle, the air space is the important factor: the bigger the gap between the water surface and the lip of the bottle, the lower the note.

Tone

Very few vibrating objects produce a pure, single-frequency sound; a tuning fork is one that does. Different instruments may make the same note, but we are able to distinguish between them because of the tone or timbre of the sound. The tone is an effect of the range of secondary sounds that are produced along with the main note; those for a trumpet are different from those for a violin. Oscilloscope traces of a trumpet and a violin will look quite different even though the frequencies of the notes being played are the same This uniqueness allows our ears to identify subtle differences, such as recognising voices or knowing which musician has played a wrong note.

Why you need to know these facts

The terminology used here is also often used in everyday speech, A knowledge of the concepts underlying the words will allow the children to use this vocabulary much more effectively,

Vocabulary

Amplitude - the strength or intensity of sound vibrations, commonly perceived as 'loudness , or 'volume' .

Frequency - the number of vibrations per second corresponding to a given sound (in musical terms, its 'pitch'), measured in hertz (Hz).

Timbre — the collection of secondary notes that accompany the main note to add richness to the sound.

Amazing facts

The highest note recorded in a human voice is 4340Hz, and the lowest is 20.6Hz - a greater range than that of a grand piano (7.25 octaves).

When the volcano Krakatoa exploded in 1883, the sound was heard 3000 miles away and four hours later was described as being like the 'roar of naval guns'.

A humpback whale can make a noise of up to 1 90dB, much louder than a jet aircraft taking off.

Common Misconceptions

Pitch and volume

Children often confuse quiet sounds and low-pitched sounds. The vocabulary needs to be exemplified carefully to ensure correct usage.