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AS PHYSICS B: Physics in
Chapter 1 revision notes…read more

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1.1 ­ Music and sound
What is sound?
· Sounds are formed by a vibration and require a medium to travel
· Sound travels as longitudinal waves (compression waves).
· Compressions: regions of HIGHER pressure than normal.
· Rarefactions: regions of LOWER pressure than normal.
· Distance between two successive waves is one wavelength.
· Frequency is number of vibrations per sec or the number of
compressions passing a fixed point in one sec.
· Frequency is measured in Hz.
· Equation for wave speed: c=f
· Sound from a musical instrument is caused by the instrument
vibrating, more vibrations means higher frequency.…read more

Slide 3

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1.1 ­ Music and sound
Detecting and measuring the frequency of sound.
· Human hearing range: 20Hz ­ 20kHz
· Sounds below 20Hz: infrasound
· Sounds above 20kHz: ultrasound
· When sounds are turned into an electrical signal with a
microphone, frequency can be measured with an
· Period: T=1/f
· (T)- Time for one vibration
· (f)- Frequency of vibrations…read more

Slide 4

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1.1 ­ Music and sound
Unique properties of sound found in music.
· Pitch: produced from fundamental frequency plus harmonics. Brain is able
to detect same pitch played by different instruments.
· Harmonics: multiples of fundamental frequency. Can be measured using
Fourier analysis.
· Fundamental frequency: the lowest frequency at which a system vibrates
· Sound waves of certain pitches when played together will produce a
consonant or harmonic.
· Octave: two notes of frequency 2:1.
· Third: two notes of frequency ration 5:4.
· Octaves and thirds are pleasant sounds.
· Timbre: quality of a sound. Made up of: harmonics; attack and decay;
· Attack of a sound: how quickly sound reaches it's peak.
· Decay of a sound: how long it takes for the sound to die away.
· Vibrato: periodic change in pitch of waveform as sound is produced.…read more

Slide 5

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1.2 ­ Listening to sounds
Representing sound waves.
· Amplitude: maximum displacement from
rest position.
· Wavelength: distance between two
successive peaks.
· Period: time length between two
successive peaks.
· Frequency of sounds can be measured on
an oscilloscope using f=1/T…read more

Slide 6

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1.2 ­ Listening to sounds
Light waves.
· Light waves do not need a medium to travel through.
· Light travels and an electromagnetic wave.
· An electromagnetic wave is a varying electric field and a
varying magnetic field which are at right angles to each
other, and to the direction of travel of the wave.
· An electromagnetic wave is a transverse wave.
· A transverse wave is one which the energy travels in a
direction at right angles to the direction of vibration.
· Speed of light = 3.0 x 10^8ms-1
· Speed of light is about a million times faster than sound.…read more

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Thank you. A great resource for comparison with my notes to check for anything missing.

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