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PHYS102

  • H4-31: VIOLIN

    H4-31
    Demonstrate some acoustical features of the violin.
    Use for show or to play, as desired. Path of vibrations from the string through the bridge, back and belly of the instrument to the air can be discussed. The soundpost and its function can be described. The overtone series can be demonstrated by touching the string at 1/2, 1/3, 1/4, 1/5, 1/6, etc. of the distance from one end while gently bowing.
    OS5

  • H4-32: VIBRAPHONE

    H4-32
    Illustrate how a vibraphone works.
    The vibraphone is an example of transverse standing waves in a bar. Tuning of the bar can be seen by looking at the undersurface. The function of the resonator can be discussed, and the vibration of the sound due to the rotating motorized baffles in the resonator tubes demonstrated.
    FS1

  • H4-33: ORGAN PIPE

    H4-33
    Illustrate how an organ pipe works.
    The pipe can be activated by blowing in the end tube, and the pitch varied by sliding the "closed" end in and out. The end of the shorter tube is open, so it produces a fixed pitch. Pipes of several lengths can be provided.
    H4

  • H4-34: GUITAR AND OSCILLOSCOPE

    H4-34
    Illustrate how a guitar works
    Play notes or chords on the guitar to see their wave shapes on the oscilloscope. Notice that as the notes decay their wave shapes change, a result of different decay times for different harmonics.
    OS5, ME2, ME3

  • H4-35: FRENCH HORN

    H4-35
    Show what a French horn and other similar instruments, such as the French horn, look like.
    This instrument is not in good condition, but is adequate for display in explaining how it works and the function of the valves, etc.
    OS5

  • H4-36: LIP-BLOWN TUBE

    H4-36
    Determine the frequencies and harmonic numbers of the resonances in a plastic tube blown like a trumpet.
    Blowing into the end of the tube as if it were a trumpet creates the odd harmonics. The lip end acts acoustically like a closed end, so in the fundamental mode the tube is one-quarter wavelength long. For this tube, the length is about six feet, so the wavelength of the fundamental is about 24 feet, and its frequency is about 50 Hz. The harmonics are then 150, 250, 350, 450, 550, etc. It is virtually impossible to sound the fundamental, but someone with a bit of finesse with brass instruments can easily demonstrate five or six overtones. Using a tube about 130cm long, seen in the photograph at the right above, the harmonics are odd multiples of 66Hz; this can be heard in an mpeg video with comparison to the frequencies of the overtone series using a Fourier synthesizer by clicking the link below.

    Tubes of different lengths can be made available upon request.
    OS0

  • H4-37: FLEXIBLE TRUMPET

    H4-37
    Demonstrate some acoustical features of the trumpet.
    Adding a trumpet mouthpiece and a funnel to the opposite ends of a flexible plastic tube creates a "flexible trumpet" which has all of the basic acoustical features of the real thing. The overtones are those of a valveless trumpet; like the trumpet, the fundamental is not good on the device. This uses the same mouthpiece as the demonstration Cornet H4-38.
    H4

  • H4-38: CORNET

    H4-38
    Demonstrate the features of a cornet.
    The cornet is virtually identical to the trumpet, except the cornet has a conical bore and the trumpet has a cylindrical bore. This creates a subtle difference in the harmonic structure between the two instruments, but their sound production, tuning, and valve configuration are the same. The cornet can be used to show the geometry and function of the valves, how they are tuned, and the notes produced by blowing the instrument with various valves pressed.
    H4

  • H4-39: PLASTIC TUBE FLUTE

    H4-39
    Show basic features of a very simple flute.
    A "flute" has been constructed using a section of thin-walled plastic. Finger holes have been crudely positioned to obtain a diatonic scale, and the end near the embouchure hole has been covered with tape.

    To get the intonation reasonably close it was necessary to make the holes fairly large, so the flute may be a wee bit difficult to play if you have small fingers.
    H4

  • H4-41: DRUM

    H4-41
    Demonstrate a pretty drum.
    This is an Ashiko drum, apparently similar to that pictured with Feynman. Unfortunately or fortunately, as the case may be, this one has a synthetic head. This drumhead is nicely tuned to its resonant cavity. For comparison, we have a beat-up steam-damaged older drum with a compromised resonant cavity, so it does not have as nice a tone.
    OS3

  • H4-42 RECORDER

    H2-42
    Can hear the sounds of a recorder
    This is a soprano recorder that uses German fingering. Show what a recorder looks like, how it sounds, and use it in other demonstrations illustrating the wave shape or the spectrum.
    H4

  • H4-43: UKELELE

    H4-43
    Music?
    A simple Rogue baritone ukelele, useful as an example of smaller stringed instruments.
    OS5

  • H4-51: MODULATION - AM AND FM

    H4-51
    Demonstrate AM and FM signal modulation as an introduction to vibrato and tremolo.
    The Pasco Dual Function Generator is used to produce either amplitude modulation or frequency modulation using various combinations of sine, triangular, and square waves. Frequency modulation is pure vibrato and amplitude modulation is pure tremolo; actual vocal vibrato is a combination of pure vibrato and pure tremolo.
    H4, ME2

    h4-51ah4-51b

  • H4-55: YAMAHA DX7S DIGITAL SYNTHESIZER

    H4-55
    Demonstrate features of a modern digital synthesizer.
    This device is a modern digital synthesizer. An enormous number of functions and effects can be illustrated using this instrument. Please see Demonstration Reference File for manuals on its operation and features.
    OS5, ME3

  • H5-01: EAR MODEL

    H5-01
    Illustrate the parts of the ear, their spatial relationships, and their functions.
    This model nicely shows how the major organs of the ear are physically arranged. The bone chain, the cochlea, and the semicircular canal assembly are removable. The fact that space is three-dimensional leads to the necessity of three orthogonal semicircular canals, which can easily be seen. The interesting parts in the middle and inner ears are shown in the close-up photograph.
    H5

  • H5-11: WAVETEK AND AUDIOCART - FREQUENCY RANGE OF HEARING

    H5-11
    Demonstrate the approximate frequency range of human hearing.
    The audio system has a useful range from below 20 Hz through well above 20 kHz, although it doesn't do well below about 40Hz. Have people raise their hands when they hear the tone to see the hearing range of the group. Note also that, keeping the intensity constant while sweeping from 1 kHz to 10 kHz, people hear the tone as louder around 3-5 kHz because the ear is most sensitive in that frequency range. Invite student discussion of why different people may have slightly different hearing ranges, and how that affects us in everyday life. How can this information be used to improve accessibility and inclusivity?
    FS1

  • H5-12: WAVETEKS AND AUDIO CART - CRITICAL BAND

    H5-12
    Demonstrate the effect of the critical band on the sound of two simultaneous sine waves.
    Set the two oscillators to equal amplitudes and the amplifier in monaural, with one at 500 Hz. Starting at less than 100 Hz, sweep the frequency of the second oscillator slowly past that of the first oscillator. When the two oscillators come within about 20 percent in frequency, a coarseness can be heard. This coarseness arises from the overlap of the critical bands of the two tones. Moving the two frequencies closer creates beats.

    Note that these frequencies are chosen to provide an easily audible demonstration; critical bandwith varies significantly with frequency.

  • H5-13: WAVETEKS AND AUDIOCART - MASKING

    H5-13
    Demonstrate masking.
    The first oscillator, the "masking" tone, is set to a 500 Hz sine wave at medium intensity. The second is to be the "masked" tone, which will be varied in frequency and in intensity. The second tone is easily masked when its frequency is higher and its amplitude lower than the masking tone. Masking occurs very readily when the second tone is up one octave, twice the frequency of the masking tone. Frequencies below the masking tone are not easily masked, even at relatively low amplitudes.

    Masking phenomena are significant in understanding the process of hearing. When analyzing a complex sound, it is notable that masked components can be altered or removed without substantially changing the experience of hearing.

  • H5-16: OHM'S LAW OF HEARING - FOURIER SYNTHESIZER

    H5-16
    Validate Ohm's Law of Hearing for a simple case.
    Form a complex tone from the first and second harmonics, with the amplitude of the second harmonic about half that of the first and a fundamental frequency of about 200-500 Hz. Changing the phase of the second harmonic changes the wave shape but leaves the sound virtually unchanged. This is Ohm's Law of Hearing: That the relative phase of components of a sound is, under normal circumstances, undetectable to our ears. Like Ohm's law of electrical resistance, it is not a universal law of nature, but a description relevant to many common phenomena.

  • H5-19: SUM AND DIFFERENCE TONES

    H5-19
    Quantitatively demonstrate sum and difference tones.
    Set the two oscillators to equal amplitudes with frequencies of 500Hz and 700 Hz, so that the combination tones are not masked by being related harmonically. When the volume of the system is turned sufficiently high, several difference tones will immediately be heard: 200 Hz, 300 Hz, and 400 Hz. Move the frequency of one of the oscillators back and forth by a small amount to call attention to the difference tones. The extra oscillator and speaker can be set to the difference frequency so that it can be identified by the observer. Sum tones also occur, the best example being at 1200 Hz, but it cannot be heard due to masking by the two louder original tones. However, tuning the extra oscillator to a frequency of 1200 Hz at a low a amplitude will allow it to beat with the sum tone, thus indicating that the sum tone is actually there!
    FS1, ME3