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Day 6 Exam I is on Thursday. Be sure to attend lab this week.

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Presentation on theme: "Day 6 Exam I is on Thursday. Be sure to attend lab this week."— Presentation transcript:

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2 Day 6 Exam I is on Thursday. Be sure to attend lab this week.

3 Review u Use the review sheet online. u Work out the online quiz. u Read the chapters and review the homework.

4 u Beats - the periodic variation in loudness of two sounds played together u The beat frequency is equal to the difference in the frequency of the two sounds. u What is the beat frequency when a 262 Hz and a 266 Hz tuning fork are sounded together? Beats

5 Radio Broadcasts u Modulation - an impression of the sound wave on a higher frequency radio wave u AM Amplitude Modulation 535 kHz to 1605 kHz u FM Frequency Modulation 88 MHz to 108 MHz

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7 Chapter 21 Musical Sounds

8 Noise Versus Music u What is the difference between noise and music? Answer: The appearance of the waveform. Mac Mic

9 NOISE VERSUS MUSIC

10 Pitch... u … is the "highness" or "lowness" of a tone. u Pitch corresponds to frequency. u Concert A on the Musical Scale has a frequency of 440 Hertz.

11 Major Scale Letter Frequency Frequency Note Name (Hz) ratio Interval do C 264 9/8 Whole re D 297 10/9 Whole mi E 330 16/15 Half fa F 352 9/8 Whole sol G 396 10/9 Whole la A 440 9/8 Whole ti B 495 16/15 Half do C 528

12 Quality... u …is the characteristic sound that allows us to distinguish between two musical instruments.

13 Same Note - Different Instrument

14 u Harmonic a partial tone that is an integer multiple of the fundamental frequency u Fundamental Frequency the lowest frequency of vibration a.k.a. the first harmonic

15 Harmonics u Harmonics on a Guitar String u Harmonics in an Organ Pipe Open on one end, close on the other Open on both ends

16 Back

17 Fourier Analysis... u …is a mathematical method that will resolve any periodic wave form into a series of simple sine waves. u See Figure 20.9.

18 Back

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21 Sound Intensity and Loudness u Intensity of Sound refers to the amplitude of the pressure variations in the sound wave

22 u Loudness the physiological sensation directly related to the sound intensity measured in bels 1bels = 10 decibels

23 u Loudness A sound of 10 decibels is or 10 1 or 10 times as intense as 0 decibels. 20 decibels is 10 2 or 100 times the intensity 0 decibels. How much more intense is sound at 100 dB than sound at 50 dB? –Answer: 100000 times

24 Source of SoundLoudness (db) Threshold of Hearing0 Conversation60 Ear Damage Begins85 Amplified Music110 Jet Airplane at 30 meters140

25 Review Questions

26 Day 7 Exam I is on Tuesday.

27 Back

28 COMPACT DISCS  Phonograph players give analog signals.  Digital signal is in binary code.  CD has flats and pits and is sampled 44,100 times per second.

29 1. The quality of a musical note can be changed by simply playing the note on a different instrument. (a) True (b) False

30 2. The three characteristics of a musical tone are loudness, quality, and timbre. (a) True (b) False

31 3. Frequencies of sound that are too high for the human ear to hear are called... (a) faster than the speed of sound (b) supersonic (c) infrasonic (d) ultrasonic (e) subsonic (d) ultrasonic

32 4. For the same temperature for air, does sound travel faster in humid Galveston or in dry El Paso? (a) Galveston (b) El Paso (c) same speed in either city (a) Galveston

33 5. The bending of sound through air of uneven temperature is called (a) reflection (b) refraction (c) interference (d) reverberation (e) resonance (b) refraction

34 6. Lightning is seen, then ten seconds later thunder is heard. Approximately, how far away in meters is the thunder cloud? (a) 10,500 m (b) 5280 m (c) 1050 m (d) 3400 m (e) 680 m (d) 3400 m

35 7. A 250 Hz tuning fork and a 260 Hz tuning fork are vibrating near each other. How many beats per second are heard? (a) 255 (b) 510 (c) 10 (d) 250 (e) 260 (c) 10

36 End of Section...

37 u URL - Animated Vibrating String URL u Demo - Harmonics on a Guitar u Demo - Organ Pipe u URL - Animated Organ Pipe URL

38 Common Sound Intensities


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