# THE PHYSICS OF MUSIC ♫. MUSIC Musical Tone- Pleasing sounds that have periodic wave patterns. Quality of sound- distinguishes identical notes from different.

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THE PHYSICS OF MUSIC ♫

MUSIC Musical Tone- Pleasing sounds that have periodic wave patterns. Quality of sound- distinguishes identical notes from different instruments. http://www.animations.physics.unsw.edu. au/jw/sound-pitch-loudness-timbre.htm

Beats- the change in sound intensity due to the interference of sound. Beat Frequency- the number of maximum intensity points per second. 2 beats

Ex. A sound with a frequency of 400Hz interferes with a second sound. If this produces 20 beats in 5.0 seconds, what is the frequency of the second sound? BF= 20beats/ 5 sec = 4 beats/sec 4 beats/sec = | 400Hz- f 2 | = 396Hz or 404Hz BF = # beats or BF = | f 1 – f 2 | second

STANDING WAVES Two identical waves traveling in opposite directions. N –node A- antinode

MODES OF VIBRATION Fundamental mode, lowest pitch. λ = 2L First overtone, second harmonic, λ = L Second overtone, 3 rd harmonic, λ = 2/3L Third overtone, 4 th harmonic, λ = 1/2L

HARMONICS Whole number multiples of the fundamental frequency. Doubling the frequency will raise the pitch one octave (8 notes)

String Instruments

LAWS OF STRINGS  Law of Length: As the length of a string increases, frequency and pitch decreases.  Law of Diameter: As the diameter of a string increases, frequency decreases.

 Law of Tension: As the tension on a string increases, frequency and pitch increases.  Law of Density: If a more dense string is used, the frequency and pitch decreases.

Woodwind and Brass Use resonating air columns to make music.

RESONANCE IN AIR COLUMNS Resonance occurs every half wavelength.

λ = 2L f 1 = v/2L L

λ = L f 2 = v/L L

λ = 2/3L f 3 =3v/2L L

Wavelength depends of the length and diameter of the resonating pipe. λ = 2( L + 0.8d) L- length (m) d- diameter (m)

Ex: An open plastic pipe will resonate at its lowest frequency when a tuning fork is held over it. A)If the pipe has a length of 60cm and a diameter of 4.0cm what is the wavelength? λ = 2( L + 0.8d) λ = 2(0.6m + 0.8(0.04m) λ = 1.264m

B) If the sound produced has a speed of 342m/s, what is its frequency? (Lowest frequency is the 1 st harmonic.) f 1 = v/2L f 1 = 342m/s / (2 x 0.6m) f 1 = 285 Hz