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JND (dB) 1.5 200 Hz 0.5 1000 Hz 40 80 Sound Intensity Level (dB) If a singer has trouble holding the loudness of a note perfectly, but she still wants to impress her audience with a demonstration of steady loudness, it’s better for her to: A) Sing quietly and low pitched B) Sing quietly and high pitched C) Sing loudly and low pitched D) Sing loudly and high pitched JND (dB) 8 kHz 200 Hz 1000 Hz 40 80 Sound Intensity Level (dB) If a singer has trouble holding the loudness of a note perfectly, but she still wants to impress her audience with a demonstration of steady loudness,, it’s better for her to A) Sing quietly and low pitched B) Sing quietly and high pitched C) Sing loudly and low pitched D) Sing loudly and high pitched E) Something else SIL (deciBels) 100 0 100 1000 Frequency (in Hz) 10k What loudness and frequency are at this point indicated by the dot and arrow on the graph? A) 100 Hz, 100 dB B) 1000 Hz, 100 dB C) 10,000 Hz, 100 dB D) 1000 Hz, 50 dB E) 100 Hz, 50 dB SIL (deciBels) 100 50 phon 0 phon 0 100 1000 Frequency (Hz) 10k Pick the correct interpretation of the Fletcher-Munson graph: A) Low pitches (around 100 Hz) are harder to hear than medium pitches (around 1 kHz). B) Medium pitches (around 1 kHz) are harder to hear than low pitches (around 100 Hz). C) High pitches (around 10 kHz) are harder to hear than medium pitches (around 1 kHz). D) Medium pitches (around 1 kHz) are harder to hear than high pitches (around 10 kHz). E) More than one of the above is correct. Phys 1240: Sound and Music Reminder: help reduce distractions during lecture Please Turn off cell phones Put away laptops Put away newspapers or other reading Stop side conversations Don’t leave in last 5 minutes of class Phys 1240: Sound and Music www.colorado.edu/physics/phys1240 LAST TIME: Ears and Hearing. TODAY: Hearing and sound perception NEXT TIME: Standing waves and elements of music READ: 10.1. Start 7.1, 7.2 • Homework 8 and Reading Question 10 due tonight. • RQ 10: what topics should be covered in the last part of the course? • Homework 9 and Reading Question 11 due next Thursday. • http://www.cochle a.org/ (Ear) • Positiondependent resonance! Fletcher-Munson graph: contours of constant loudness 100 SIL (deciBels) 100 50 0 phon 0 100 Frequency (in Hz) 1000 10k Clicker question You’re listening to a 50 dB sound at 1000 Hz. If you want to listen to much lower pitches, feeling the “same loudness” to you, should the SIL (in dB) of the lower frequency sound be… A) HIGHER than 50 dB B) LOWER than 50 dB C) Still 50 dB The topographic map (elevation contour) of a farm is shown: 25’ 20’ 15’ 10’ What does it mean when the contours are close together, as seen just right of the windmill? A) The hill is steeper where the contours are closer together. B) The hill is flatter where the contours are closer together. C) There is no hill where the contours are closer together. 25’ 20’ 15’ 10’ Far apart contours: Close together contours: small motion produces small motion produces small change. big change. Fletcher-Munson graph 100 SIL (deciBels) 100 50 0 phon 0 100 Close together Frequency (in Hz) contours 1000 Far apart contours 10k Clicker question Which will seem like (be perceived as) a bigger increase in loudness? (Assume that the sound starts off loud enough to be audible.) A) Increasing by 50 dB, while listening to 50 Hz sound B) Increasing by 50 dB, while listening to 1000 Hz sound C) Both seem “equally more loud” Fletcher-Munson graph 100 SIL (deciBels) 100 50 0 phon 0 100 Frequency (in Hz) 1000 10k Clicker question Music is recorded at a loud concert. You play it at home, and turn down the volume (reducing ALL frequencies by the same # of dB) How will it sound? A) Same, just quieter B) Low frequencies will be over-emphasized (“bass-y”) C) Low frequencies will be under-emphasized (“treble-y”) Fletcher-Munson graph 100 SIL (deciBels) 100 50 0 phon 0 100 Frequency (in Hz) 1000 10k Clicker question Music is recorded at a soft concert. You play it at home, and crank the volume (increasing ALL frequencies by the same # of dB) How will it sound? A) Same, just louder B) Low frequencies will be over-emphasized C) Low frequencies will be under-emphasized Fletcher-Munson graph 100 SIL (deciBels) 100 50 0 phon 0 100 Frequency (in Hz) 1000 10k Fletcher-Munson graph Range of Hearing Sound Level (dB) My hearing response curve http://www.phys.unsw.edu.au/jw/hearing.html New (old!) topic: Standing waves • What do they look like? Standing wave • How can you make one? Wave on a string •How can we describe them? Standing waves L The “fundamental” vibration Also called the "first harmonic” http://phet.colorado.edu/simulations/sims.php?sim=Wav Amplitude: 29, Frequency: 9, Friction: 5 A string is clamped at both ends and then plucked so that it vibrates in a standing wave between two extreme positions a and c. (Let upward motion correspond to positive velocities.) When the string is in position b, the instantaneous velocity of points along the string is... A: zero everywhere. B: positive everywhere. C: negative everywhere. D: depends on position.
