Physics 1251 The Science and Technology of Musical Sound Unit 1 Session 10 Fundamentals of Sound Review Unit 1 Session 10 Fundamentals of Sound Review

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Foolscap Quiz: Three students push a heavy box across the floor. If together they exert a force of 1000 Newtons and they move it by 3.6 meters, how much work did they do? If they were able to move it that far in one minute (60. seconds) what power did they expend? W=F ‧ d = (1000. N)(3.6 m)= 3600 J = 3.6 kJ; Power = W/t = 3600 J/60 s = 60 W.

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review 1′ Lecture: Knowledge is of at least three (3) kinds: Knowledge is of at least three (3) kinds: Concepts—understand them.Concepts—understand them. Facts—know them.Facts—know them. Skills—practice them.Skills—practice them. Sound transmits energy through a material medium in the form of a pressure- displacement wave, originates from an oscillator or other disturbance, and is characterized as a combination of sine waves of various frequencies. Sound transmits energy through a material medium in the form of a pressure- displacement wave, originates from an oscillator or other disturbance, and is characterized as a combination of sine waves of various frequencies.

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Concepts: Sound is a longitudinal pressure/ displacement wave that propagates through a material medium in the range 20 to 20 kHz. Sound is a longitudinal pressure/ displacement wave that propagates through a material medium in the range 20 to 20 kHz. Sound waves originate from oscillators. Sound waves originate from oscillators. Complex repeating motion can be analyzed as a combination of simple harmonic motions. Complex repeating motion can be analyzed as a combination of simple harmonic motions. A Simple Harmonic Oscillator oscillates in sinusoidal motion with a single well-defined frequency. A Simple Harmonic Oscillator oscillates in sinusoidal motion with a single well-defined frequency.

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review ⃒⃖ λ ⃒⃗ Wavelength ⃗ ⃖ ⃖ ⃗ V ⃗ ⃗ ⃗

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Oscillating Hand Demonstration ☞♫Compression Rarefaction

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Simple Harmonic Oscillators Helmholtz Resonator Helmholtz Resonator

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Spring ———→ Mass ————→ Two Masses on Two Coupled Springs Spring ————→ Mass ————→ Mode 1 Mode 2

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review 80/20 A Fourier Analysis is a representation of all the components that comprise a waveform, amplitude versus frequency and phase versus frequency.

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Example: Synthesis of a Square wave- The Fourier Spectrum Frequency fofofofo 3f o 5f o 7f o 1 st Overtone – 3 rd Harmonic 2 nd Overtone – 5 th Harmonic Fundamental – 1 st Harmonic Amplitude

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review

Concepts: Sound transmits energy. Sound transmits energy. The energy of an oscillator or of sound dissipates in an exponential decay. The energy of an oscillator or of sound dissipates in an exponential decay. The timbre of an instrument changes with time because of the transients. The timbre of an instrument changes with time because of the transients. An oscillator can be caused to vibrate in “sympathy” when the driving frequency is close to that of a natural mode of oscillation. An oscillator can be caused to vibrate in “sympathy” when the driving frequency is close to that of a natural mode of oscillation.

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review “Exponential Decay” E = E o /2 t /t 1/2

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Time Dependent Fourier Spectrum: Observe Transients Piano Transient Frequency Spectrum Frequency Amplitude of Component

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review ADSR: Attack, Decay, Sustain, Release The “envelop” of the amplitude of all musical sound Is described by ADSR. Attack Decay Sustain Release

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review “Resonantly Driven” Simple Harmonic Oscillator

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Facts: Definitions: SoundSound Longitudinal waveLongitudinal wave Transverse waveTransverse wave PressurePressure DisplacementDisplacement PeriodPeriod FrequencyFrequency WavelengthWavelength Non-dispersiveNon-dispersive

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Facts: Definitions: Simple Harmonic OscillatorSimple Harmonic Oscillator Spring constantSpring constant Helmholtz ResonatorHelmholtz Resonator Normal Mode of oscillationNormal Mode of oscillation DegeneracyDegeneracy Fourier Analysis and SynthesisFourier Analysis and Synthesis Harmonic seriesHarmonic series FundamentalFundamental OvertoneOvertone MicrophoneMicrophone OscilloscopeOscilloscope

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Facts: Definitions: Sine waveSine wave SinusoidalSinusoidal AmplitudeAmplitude PhasePhase Ohm’s LawOhm’s Law IntervalInterval TimbreTimbre WaveformWaveform TransientTransient

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Facts: Definitions: Definitions: WorkWork EnergyEnergy PowerPower IntensityIntensity TransientTransient ResonanceResonance PrecisionPrecision AccuracyAccuracy Significant figureSignificant figure Logical InductionLogical Induction

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Facts: Important Prefixes: Mega- ( M) = = 10 6 kilo- ( k) = = 10 3 centi- ( c) = 1/100 = milli- ( m) = 1/1 000 = micro- (μ) = 1/ = 10 -6

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Scientific Notation A number can be written as the product of two numbers: the first (mantissa) is a number 1 or more but less than 10; the second is 10 to a power (the exponent) that puts the decimal in the correct place. Negative powers mean 1/10 to the power (e.g = 1/10 3 ). For example: Big Numbers: x 10 3 = Small Numbers: x 10 –2 =

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Know your calculator: Enter: “ EXP” or “EE” “03” You will read “ ” or “ E03” Enter: “ EXP 03 +/- or (-)” You will read “ ” or “ E-03”

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Vademecum (take with me) : v = d /t(also d = v∙t and t = d /v ) v = d /t(also d = v∙t and t = d /v ) p = F /A p = F /A ρ = m/V ρ = m/V P = 1/ f P = 1/ f v = λ ⋅ f v = λ ⋅ f v = (T - 20 C) m/s v = (T - 20 C) m/s F = - k ‧ xf = 1/(2π) ‧ √ (k/m) F = - k ‧ xf = 1/(2π) ‧ √ (k/m) f 1 =1/P repeat f 1 =1/P repeat W =F‧d; E = W W =F‧d; E = W ℙ = W/t; I = ℙ/A ℙ = W/t; I = ℙ/A E = E o /2 t /t 1/2 E = E o /2 t /t 1/2

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Skills: Word Problem A sonar operator sends out a “ping” into the sea. He hears an echo from another submarine 4.50 seconds later. How far away is the second sub? (Essential data: the speed of sound in sea water is m/s) 4.50/2 seconds d = v t d =1500 m/s(2.25 s) d= 3.38 km

λ Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Skills: Word Problem A sound wave is emitted by a large pipe of an organ. If its frequency is approximately 65.5 Hz and the air temperature in the church is a chilly 15C, what is the wavelength of the sound wave? λ = v / f, v =? v = ( T-20) v = ( 15-20) v = 343 – 3.0 = 340 m/s λ = v / f λ = 340 / 65.5 m λ = 5.19 m

F =2.0 n x= -.02 m Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Skills: Word Problem A 1.2 kg mass is mounted on a thin steel rod. If when I press on the rod with a force of about 2.0 N is deflects to the side by about 2.0 cm, at what frequency will the mass oscillate if I pluck it? f = (1/2π)√(k/m), k =? k = -F/x = 2.0 N/0.02 m = 100 N/m f = (1/2π)√(k/m) = (1/2π)√(100/1.2) f = (.1592)√(83.3)= 1.45 Hz

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Skills:Analysis When John fills a jug with water he notices that the pitch of the splashing noise that he hears rises as the jugs fills. Why is that ? (1) Higher pitch means higher frequency. (2) The jug is a Helmholtz resonator (a SHO). (3) The air “spring” gets stiffer as the volume gets smaller, i.e. k get larger. (4) Therefore, since f ∝ √k for a SHO, f gets higher.

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Skills: Analysis How can you know that the speed of sound in air is non-dispersive? (1) “ Non-dispersive” means that the speed does not depend on frequency. (2) When a person speaks, his voice contains many frequencies. (3) If the speed depended on frequency, the timbre of the voice would change as you got farther away from a person. It doesn’t. (4)Therefore, sound must be non-dispersive.

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Skills: Analysis Dr. M bought an acoustic ruler. How do you think it works? And what sources of error do you anticipate will affect the reading? (1)The acoustic ruler uses timing of an echo, similar to sonar, to determine the distance from the source to the reflecting surface. (2)Temperature can affect the speed of sound. But 10 C changes the speed only about 1.7%. (6/343)

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Skills: Analysis Listen to the sound bite. How do you know that the sound has been modified? (1)The transients are not correct. The sound has been played backward. (2)Now listen to sound forward.

Physics 1251 Unit 1 Session 10 Fundamentals of Sound—Review Summary of Summaries & The Cavalcade of Concepts

Physics 1251Unit 1 Session 1 Introductions Summary: To get the most out of this course use 80/20 thinking. To get the most out of this course use 80/20 thinking. The key to success is “ Attend!” The key to success is “ Attend!” Learn how you learn and do it! Learn how you learn and do it! Know your learning style(s). Know your learning style(s). Study Concepts –Facts –Skills Concepts –Facts –Skills Then take practice test

Physics 1251Unit 1 Session 2 Fundamentals of Sound Summary: Sound is a longitudinal mechanical wave that originates from a mechanical vibration and propagates in a material medium with a frequency of 20 Hz to 20 kHz. Sound is a longitudinal mechanical wave that originates from a mechanical vibration and propagates in a material medium with a frequency of 20 Hz to 20 kHz. Radio waves are E-M waves. Radio waves are E-M waves. Sound is non-dispersive. Sound is non-dispersive. The velocity of sound is 343 m/s The velocity of sound is 343 m/s at 20 C.

Physics 1251 Unit 1 Session 3 Sound Waves Summary: Pressure: p = F / A Pressure: p = F / A Standard atmospheric pressure = 101 kPa Standard atmospheric pressure = 101 kPa Frequency = number of cycles per second Frequency = number of cycles per second Hz = Hertz = cycle/second Hz = Hertz = cycle/second Period: P = 1/ f Period: P = 1/ f v = λ ⋅ f v = λ ⋅ f v = (T – 20 C) m/s v = (T – 20 C) m/s

Physics 1251 Unit 1 Session 4 Thinking as a Physicist Summary: Observe—see what is there. Observe—see what is there. Abstract—ideate the significant. Abstract—ideate the significant. Measure—compare to standard. Measure—compare to standard. Model—use math. Model—use math. Predict—risk a prognostication. Predict—risk a prognostication. Compare—check it out. Compare—check it out.

Physics 1251 Unit 1 Session 4 Thinking as a Physicist Summary (cont’d.): Units: fundamental—second, meter, kilogram; derived—Hz, N, Pa Units: fundamental—second, meter, kilogram; derived—Hz, N, Pa Scale Prefixes: M, k, c, m, μ Scale Prefixes: M, k, c, m, μ Scientific notation: x 10 3 Scientific notation: x 10 3 [1.234 E03 or ] Experimental error Experimental error Significant figures Significant figures Insufficiency of induction Insufficiency of induction

Physics 1251 Unit 1 Session 5 Simple Harmonic Oscillators Summary: A Simple Harmonic Oscillator is a device that oscillates at one frequency, determined by the spring constant k and the mass m of the system. A Simple Harmonic Oscillator is a device that oscillates at one frequency, determined by the spring constant k and the mass m of the system. The natural frequency of an SHO moving in sinusoidal motion is related to these quantities by the equation: The natural frequency of an SHO moving in sinusoidal motion is related to these quantities by the equation: f = 1/(2π) ‧ √ (k/m)

Physics 1251 Unit 1 Session 6 Helmholtz Resonators and Vibration Modes Summary: A Helmholtz Oscillator is a SHO comprised of an enclosed air volume and a narrow neck and has a single frequency. A Helmholtz Oscillator is a SHO comprised of an enclosed air volume and a narrow neck and has a single frequency. A normal or natural mode of vibration or oscillation is one of the fundamental ways that a device can move. A normal or natural mode of vibration or oscillation is one of the fundamental ways that a device can move. The number of modes is equal to the number of simple harmonic oscillators in the system. The number of modes is equal to the number of simple harmonic oscillators in the system. Degeneracy means two or more normal modes have the same frequency. Degeneracy means two or more normal modes have the same frequency.

Physics 1251 Unit 1 Session 7 Good Vibrations Summary: Waveforms can be broken down into simple sine waves, called Fourier Analysis. Waveforms can be broken down into simple sine waves, called Fourier Analysis. Waveforms can be built up from simple sine waves, called Fourier Synthesis. Waveforms can be built up from simple sine waves, called Fourier Synthesis. The lowest frequency needed is 1/P repeat. The lowest frequency needed is 1/P repeat. A Fourier Spectrum is the recipe for building the waveform. A Fourier Spectrum is the recipe for building the waveform.

Physics 1251 Unit 1 Session 8 Harmonic Series Summary: A harmonic series is the sum of sine wave components each frequency of which is an integral multiple of the fundamental frequency. A harmonic series is the sum of sine wave components each frequency of which is an integral multiple of the fundamental frequency. Ohm’s Law : humans do not sense the phase of sound directly. Ohm’s Law : humans do not sense the phase of sound directly. Intensity determines loudness Intensity determines loudness Frequency determines pitch. Frequency determines pitch. Waveform (harmonic series) determines timbre. Waveform (harmonic series) determines timbre. An octave interval corresponds to a frequency ratio of 2 : 1. An octave interval corresponds to a frequency ratio of 2 : 1.

Physics 1251 Unit 1 Session 9 Transients and Resonances Summary: Transients occur because radiation and friction damp the various harmonics differently. Transients occur because radiation and friction damp the various harmonics differently. Resonance is the phenomenon of sympathetic vibration at a natural frequency with energy supplied by an outside source. Resonance is the phenomenon of sympathetic vibration at a natural frequency with energy supplied by an outside source. Sound transmits energy since pressure = force/area and a displacement occurs as a sound wave passes. Sound transmits energy since pressure = force/area and a displacement occurs as a sound wave passes.