Physics 167 Final Study Review PDF

Physics 167 Unit I Review Sheet 1. Understand how force, pressure, energy, power and intensity are defined and how they are related to sound waves. Force: Force= Distance/ Displacement (N). Pushing or Pulling. Pressure: Pressure= Force/ Area (N/m^2(Pa)). Weight often in pounds (lbs). Energy: PE and...

Physics 167 Unit I Review Sheet 1. Understand how force, pressure, energy, power and intensity are defined and how they are related to sound waves. Force: Force= Distance/ Displacement (N). Pushing or Pulling. Pressure: Pressure= Force/ Area (N/m^2(Pa)). Weight often in pounds (lbs). Energy: PE and KE. PE is stored energy and KE is motion energy (J). Power: Power= Energy/ Time (J/s(W)). How fast you climb up the stairs. Intensity: Intensity= Power/ Area (W/m^2). Like loudness. 2. Compute the natural (resonance) frequency of a simple vibrator using its period of vibration. 3. Describe how changes in a simple vibrator’s mass, stiffness, and resistance change the frequency and decay rate of the vibrator. Increasing the mass on a simple vibrator results in a lower frequency, and decreasing mass results in a higher frequency. More stiffness results in a higher frequency, and less stiffness results in a lower frequency. With more or less resistance (damping) the natural frequency doesn’t change, but the amplitude will. 4. Identify the displacement, speed, kinetic energy, and potential energy of a simple vibrator at each point on a graph of displacement v. time.  5. When given the natural frequency of a simple vibrator, calculate the driving frequency that will cause the vibrator to achieve its greatest amplitude. It will be one of its natural frequencies. Frequency= 1/T or V/λ 6. Describe how different parts of a string fixed at both ends vibrate in relation to each other (including phase, amplitude, and frequency) when the string vibrates in its first, second, third, fourth, and fifth natural modes. F1: In phase, amplitudes different, same frequency. F2,3,4,5: Out of phase, amplitudes different, same frequency. 7. Identify the diagram representing a string’s motion when driven at first, second, third, fourth, or fifth natural frequency. Identify the number of nodes and number of antinodes. Frequency spectrum. When fixed at both ends: F1: 2 nodes 1 antinode F2: 3 nodes 2 antinodes F3: 4 nodes 3 antinodes F4: 5 nodes 4 antinodes F5: 6 nodes 5 antinodes 8. Identify the amplitudes of each mode from a diagram of a vibration’s spectrum. 9. Understand the difference between transverse and longitudinal waves including the direction of motion for particles compared to the direction the wave is traveling in and which media each type of wave can travel/propagate in. Transverse waves can only occur in solids Longitudinal waves can occur in solids, liquids, and gases 10. Identify the type of wave present (transverse or longitudinal, drive or free) and the medium (solid, liquid, or gas) in which it travels when given an example of a wave. Sound wave when you hit a drum On the surface of the drum there is transverse waves, but through the air they are longitudinal Sound you hear is a longitudinal wave Wave on a guitar string is a transverse 11. Calculate the wavelength of a longitudinal wave when given the distance between condensations or rarefactions. The distance between a condensation and a rarefaction is half a wavelength, so you would double it for the full wavelength. 12. Describe how changes in density and tension of a string affect wave speed in that string. When tension increases wave speed increases When density increases wave speed decreases Wave speed decrease by decreasing tension and increasing mass/length v=sqrt(tension/(mass/length)) Waves move faster in warmer air Wave speed is independent of freq. 13. Identify common acoustical examples of diffraction, reflection, refraction, Doppler shift, and absorption. Diffraction: Sound bends around objects and spreads out through an opening Reflection: Specular reflections bounce off the same angle as incident, Diffuse reflections scatter. Refraction: Direction sound travels changes with change in medium. Doppler shift: Moving sound source changes the frequency Absorption: Sound waves can be absorbed in materials Diffraction is when waves bend around a corner, and spread out when going through an opening. Low frequencies do it better. Refraction is when waves change direction in a medium. Echo:reflection delayed by >50 ms 14. Calculate the distance to an object when given the time delay between an initial sound and its returning echo from the object. 15. Describe the path of sound through air layers of differing temperatures. Identify which air layer conditions will allow sound to be heard over long distances on the ground and which will not. Refraction Warmer air speeds up the wave, while colder slows it down. During the night sound refracts down and skips along the ground making it able to be heard further away. Sound is easier to hear at further distances during the night because sound refracts downward (ground cooler) Sound is harder to hear at further distances during the day because sound refracts upward (ground warmer) 16. Calculate the Doppler shift when given the initial frequency of a sound source and the speed with which a moving listener approaches or retreats from the source. 17. Calculate the beat frequency when given two simultaneous sine waves. 220Hz-221Hz= 1Hz (beat frequency) 18. Identify possible end conditions of a string or tube when given a diagram of its wave pattern. 19. Calculate the natural frequencies of the first two modes of a string fixed at both ends when given the length of the string and the wave speed in the string. 20. Calculate the natural frequencies of the first two modes of an air-filled open-open tube and an air-filled closed-open tube when given the length of the tube. Open open: v/2L, all Open closed: v/4L, odd Resonance frequency of vocal tract is the formant frequency (closed and open) Resonance frequency of ear canal is the formant frequency (closed and open) v=340 (air) 21. Given a list of frequencies, determine whether a given upper partial is harmonically or inharmonically related to the fundamental. Identify which is the fundamental or first partial and which are the second, third, fourth, etc. partials. 10Hz, 20Hz, 25Hz, 30Hz, 35Hz Inharmonic (35/10=3.5 (not integer)) Fundamental (lowest natural frequency) is 10Hz 22. Identify whether a partial on a spectrum diagram is harmonic or inharmonic.  Quasi inharmonic Harmonic Harmonic: must be multiples of fundamental Inharmonic: are not multiples of fundamental 23. Describe the key elements of a complex periodic and complex non periodic wave (including harmonicity of the partials with respect to the fundamental frequency). A complex periodic wave has multiple sine waves added together where each frequency mode is harmonic with the fundamental (integer multiple) A complex non periodic wave has multiple sine waves added together but all of the mode frequencies aren’t integer multiples of the fundamental, it is inharmonic. 24. Given an acoustic pressure at a specified distance from a source, calculate the acoustic pressure at ¼, ½, twice, and four times the specified distance. 200Pa at 10m from source 4x: 40m = 50Pa 2x: 20m = 100Pa ½x: 5m = 400Pa ¼x: 2.5m = 800Pa 25. Calculate the sound pressure level (relative to 20 μPa) when given an acoustic pressure μPa. SPL= 20log (p/Pref) 10 300,000,000µPa SPL=20log (300,000,000µPa/20µPa) 10 SPL= 143.52 dB 26. Given a sound pressure level at a specified distance from a source, calculate the sound pressure level at ¼, ½, twice, and four times the specified distance. 140 dB at 10m from source 4x: 40m = 140-6-6= 128dB 2x: 20m = 140-6= 134dB ½x: 5m = 140+6= 146dB ¼x: 2.5m = 140+6+6= 152dB 27. Identify sound pressure levels on the A-weighted scale associated with common sounds (threshold of hearing, a whisper, normal conversation, a lawnmower, traffic on a busy street, threshold of pain, etc.). Threshold of Hearing: 0 dBA Whisper: 20 dBA Normal Conversation: 60 dBA Traffic on a Busy Street: 70 dBA Lawnmower: 90 dBA Threshold of Pain: 140 dBA All sound levels above ~85 dB are going to be damaging 28. Identify the forms of energy received and generated by common transducers including microphones, magnetic pickups, the human voice, the human ear, a CD player, etc. Microphones: receive=>acoustic generate=>electric Magnetic pickups: receive=>mechanical generate=>electric Human voice: receive=>physiological generate=>acoustical Human ear: receive=>acoustical generate=>physiological CD player: receive=>optical generate=>electrical 29. Identify the functions of common devices such as an oscilloscope, a microphone, an A/D converter (ADC) or D/A converter (DAC), a spectrum analyzer, etc. (i.e. – What form of signal do they convert from and to?). Oscilloscope: Takes electrical signals and converts them to a Time Waveform Microphone: Takes acoustic signals and converts them to electric signals in time-varying voltage ADC: Takes analog signals and converts them to digital signals DAC: Takes digital signals and converts them to analog signals Spectrum analyzer: Takes electrical signals and converts them to a Frequency Spectrum 30. Identify the purpose of an instrumentation system when given a block diagram of the system. This instrumentation system is plugged into a power supply that then converts that energy using a transducer to an electrical signal that is then amplified and put into a record where it can either be put into a controller of a data processor. 31. Identify which materials (passive, porous, light weight, absorptive, or airtight) will best exclude external noise or limit internal noise. Absorptive and airtight materials will exclude external noise best. Absorptive, porous, and lightweight materials will limit internal noise. External sounds: walls to be airtight, walls to be massive, distance, vibration isolation Internal sounds: absorption (porous and lightweight materials) 32. Describe and give examples of echoes, flutter echoes, dead spots, sound shadows, and sound focusing in an auditorium. Echos: Reflected sounds arriving more than 50ms later than direct sound. Flutter echoes: Rapid succession of small echoes. Dead spots: Nodes in the room where no sound is heard Sound shadows: Direct sound but little reflected sound. Sound focusing: Caused by curved surfaces, high in some places low in others. 33. Understand how the reverberation time in a room depends on volume and absorption. For a sample room made of specified materials, calculate the total absorption coefficient and the approximate reverberation time. v=800m3 s=850m2 Brick on all walls, 50 people, 2000 Hz, AC=0.05 TAwithout people= S*AC =42.5 RTwithout people= 0.16*v/TA =3.0s TAwith people =.55*50 people + 42.5= 70m2 RTwith people= 0.16*v/TA =1.8s When you add people to a room the RT goes down 34. Compare desirable reverberation times for speech, opera, chamber music, orchestral music, and organ music in large and small auditoriums. Short RT ⇩ Long RT 35. Determine which perceptual characteristics (spaciousness, intimacy, warmth, loudness, clarity, ensemble, or reverberance) depend most strongly on early reflections after the direct sound, overall sound level, a large ratio of early to late reflection energy, early reflections from a stage enclosure, whether the sound that the left and right ears hear are the same, the degree of bass frequencies, or reverberation time in the concert hall. Spaciousness = BQI -Whether the Sound that te Left and Right Ears Hear are the Same Intimacy = ITDG -Early Reflections After the Direct Sound Warmth = EDT -Degree of Bass Frequencies Loudness = Strength -Overall Sound Level Clarity = Early/Late Ratio -A Large Ratio of Early to Late Reflection Energy Ensemble = Early Reflections from a Stage Reverberance = Reverberation Time 36. When given a block diagram of a sound reproduction system, identify the type of signal (electrical, acoustical, magnetic, or mechanical) present at a labeled point. 1) Acoustical 2) Electrical 3) Electrical 4) Electrical 5) Electromagnetic 6) Optical 37. Identify what best reduces feedback in a sound reinforcement system when using a microphone. Moving the mic closer to talkers mouth Moving loudspeaker away from mic Directional mic and loudspeaker Talker speaks loudly 38. Compare frequency response characteristics of several audio components when given a chart of their response curves. Flat curve: Balanced frequencies Peaked curve: Emphasis on certain frequencies Dipped curve: Reduction on certain frequencies 39. Understand the primary purpose for placing a loudspeaker in a baffle. To prevent the front and back sounds from canceling each other out. 40. Know whether sensitivity, bandwidth, efficiency, distortion, and dispersion are good for a loudspeaker or a microphone. Sensitivity: accuracy of ratio of an output quantity to an input quantity (More=Good) Bandwidth: Frequencies that transducer responds well to (More=Good) Efficiency: % of power converted (More=Good) Distortion: Extra noise added (More=Bad) Dispersion: Direction (Depends on Application) Physics 167 Unit II Review Sheet 1. Identify anatomical parts of the outer, middle, and inner ear on a diagram and explain their functions.  ○ Outer Ear (Transducer) Pinna The visible part of the ear that collects and directs sound waves to the ear canal. Ear Canal Leads sound waves to the eardrum Eardrum Converts sound waves into vibrations and send them to ossicles and protects middle ear ○ Middle Ear (Amplifier) Ossicles Three tiny bones (hammer, anvil, stirrup) amplify vibrations and sends them to oval window Eustachian tube Equalizes pressure ○ Inner Ear (Transducer) Oval window Opening that allows sounds into cochlea Cochlea Fluid-filled Transmits vibrations into electrical signals for the brain Basilar membrane Inside cochlea Distinguishes different frequencies of sound (higher-> lower) Pressure differences in ducts move it. Helicotrema Opening in cochlea that allows fluid to equalize Nerve fibers Transmit the electrical energy to the brain 2. Identify the part of the basilar membrane on a diagram that will vibrate most at a given frequency. ○ Low frequencies Vibrate more on the bm near the helicotrema ○ High frequencies Vibrate more on the bm near the oval window 3. Identify the processes in the inner ear that are responsible for encoding intensity, frequency, and spectrum of a sound. ○ The hair cells How many fire = intensity How many times per sec and location on BM = frequency Multiple parts get excited = spectrum  ○ High frequencies near oval window ○ Low frequencies near helicotrema ○ Complex sound, multiple parts of BM are vibrating = spectrum 4. Describe how critical band is related to masking, and how the asymmetry of the basilar membrane correlates with higher or lower tones masking each other more effectively. ○ More masking occurs within a critical band Wider CB means more masking of neighboring frequencies Tones separated less than a CB mask each other ○ The bm is asymmetrical because different frequencies vibrate different locations on the bm more ○ Low frequencies mask higher frequencies more ○ Loud frequencies mask higher frequencies more 5. Identify which of the perceptions of tone color, pitch, and loudness are related most strongly to each of the following physical quantities: spectrum, frequency, and intensity or sound level. ○ Spectrum = Tone color ○ Frequency = Pitch ○ Intensity/Sound level = Loudness 6. Calculate the loudness in phons or sones of a tone of specified frequency and sound level (in dB relative to 20 μPa). ○ Use provided table ○ What is the loudness at 500Hz at 77dB 80 phons 16 sones 7. When given several sine waves at specified frequencies, determine the fundamental frequency of the pitch that will be perceived. ○ 260Hz, 390Hz, 520Hz, 650Hz, 780Hz, 910Hz 130Hz will be perceived b/c 130 is the LCM of all the # 8. When given two simple tones of specified frequencies and at specified sound levels, determine whether they will sound perceptibly different. ○ Use provided table ○ 800Hz at 40phons ○ 805Hz at 40phons  They will be perceived as different because the JND is above the threshold 9. Identify the factor (phase, quality, intensity, pitch, or spectrum) plays the most important role in helping a listener determine from which direction a low or high frequency sound is coming. ○ Low frequency Wavelength is larger than head Phase of arrival is the most important factor ○ High frequency Wavelength is less than head Intensity at each ear is the most important factor 10. Calculate the combination tone most likely to be heard when given two simple tones of specified frequency. ○ f2-f1 ○ 255Hz and 355Hz 355-255=100Hz 11. When given two simple tones of specified frequency, determine whether the listener will perceive a single tone with no beating, a single tone with smooth beating, a single tone with rough beating, two tones with no beating, two tones with smooth beating, or two tones with rough beating. ○ Single tone no beating: Δf=0 ○ Single tone smooth beating: Δf