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 Educational Laboratory Products


Educational Laboratory Products

 

Click here for a 13-minute video
demonstrating some of the physics experiments that can be done with this equipment.

(Requires QuickTime.)

 


Sound Heads
Megahertz Thunder 
  

Sound heads (two are shown attached to a calipers above) will respond to frequencies from 5 MHz to 20 MHz. The center frequency is approximately 13 MHz. The sound heads have a slot and screw so that they can be mounted on a calipers or any other 1/8 inch thick material. The emitted sound is a 2 mm wide beam perpendicular to the front face of the head. In the picture the sound travels from one head to the other. The beam emerges from near the bottom of the head.

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Pulser Box
Pulser Box  
  

The IDP Pulser Box is one way to excite the Sound Heads. It puts out a very short, high Voltage pulse. When connected to the Sound Heads, it results in a short pulse of ultrasound with a Fourier transform center frequency of around 13 MHz. A second output is a low Voltage pulse which occurs at the same time as the high Voltage pulse. It can be used as a time reference or oscilloscope trigger. A 12 Volt external power supply is included.

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Protractor Table
Protractor Table  
  

The Protractor Table is used for the acoustical refraction and diffraction experiments. It consists of a rotatable support table with a protractor to measure the angles of the transmitter and receiver Sound Heads, and a swing arm mounting for the receiver Sound Head.

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Needle Hydrophone
Hydrophone with interchangable tips
Hydrophone in use
Beam pattern of a sound head measured with the hydrophone

Needle Hydrophone Description  
 

The IDP Needle Hydrophone is a new product designed for both educational and research laboratories. Well-suited for ultrasonic field mapping and for measuring the frequency response of transducers, this low-cost device can be used with one of two available probe tip sizes: 1.0mm and 0.5mm.

Click here for details and specifications.

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Experiments - One Instrument, Many Experiments

Many physics experiments can be done with the Sound Heads. Below is a list of several of them, along with a brief description and a list of the equipment required. A kit is available from IDP for each of the experiments.In addition, all of these experiments require the use of an oscilloscope, BNC patch cables, and some laboratory stands and rods.


Speed of Sound Experiments  

The speed of sound can be measured in liquids, solids, and gases. The setup is two Sound Heads attached to a calipers, one of them is driven by the Pulser Box, the other is attached to an oscilloscope. With the short rise time from the Pulser Box, the time delay from excitation to reception in liquid can be measured very accurately on the oscilloscope. The calipers gives the distance involved, and the ratio is the sound speed.

For a solid sample in water, the difference in time delay, delta(t), between the solid being in or out of the sound path is used with the sample length in the formula Vs = 1/(1/Vw – delta(t)/L) to give sound speed, where Vw is the speed of sound in water, delta(t) is the time delay difference, and L is the sample length.

Speed of Sound Equipment

Required:

  • two Sound Heads (left and right)
  • one Pulser Box with power supply

Accessories included in the kit:

  • material samples of aluminum, copper, and polycarbonate
  • a petri dish
  • one calipers with support rod

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Acoustical Refraction Experiments

Acoustical Refraction can be measured with a Protractor Table and swing arm similar to a spectrometer, with Sound Heads in place of optics. The arrangement is similar to a prism spectrometer experiment. The aluminum, or other solid, is not acoustically dispersive as is a prism for light, instead what is measured is the refracted signal for the longitudinal wave and the shear wave. With these results, and the density of the aluminum, all of the elastic constants can be calculated.

Acoustical Refraction Equipment

Required:

  • two Sound Heads
  • one Pulser Box with power supply
  • one Protractor Table

Accessories included in the kit:

  • material samples of aluminum, copper, and plastic
  • a petri dish
  • several thin plate samples for the thin plates part of the experiment

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Acoustical Diffraction Experiments

Acoustical Diffraction can also be measured on the Protractor Table. The acoustical diffraction grating shown in the picture can be placed in the center of the Protractor Table, oriented perpendicular to the path of the beam, and the receiver Sound Head used to measure the emerging field pattern as a function of angle. Likewise, field patterns of single or multiple slits can be measured.

Acoustical Diffraction Equipment

Required:

  • two Sound Heads
  • one Protractor Table
  • one burst generator

    The signal source for this experiment is a burst generator. IDP does not supply this generator, but will give suggestions on which commercially available generators are adequate.

Accessories included in the kit:

  • one acoustical diffraction grating
  • several acoustical single slits
  • a petri dish
  • an acoustical beam expander

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Acousto-optic Experiments

Acousto-Optical devices are usually made of a material like tellurium because they have a large acousto-optic coefficient; however, water has an acousto-optic effect large enough to be used in a laboratory experiment. With the IDP Sound Heads, a simple acousto-optic modulator can be made with any laser with a beam diameter less than 2 mm, a water tray, Sound Heads, and a signal generator.

Acousto-optic Equipment

Required:

  • two Sound Heads
  • one water tray
  • a source of 8 to 16 MHz at 30 Vp-p. (If the source is not capable of at least 30 Vp-p, an amplifier will be necessary.)
  • a laser
  • condensing optics

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Acoustical Etalon Experiments

An acoustic etalon is based on the same principle as an optical etalon; namely, that multiple reflections add when the spacing is such that they all arrive at the second boundary in phase. A function generator is connected to one Sound Head. The frequency of the function generator must be within the operating range of the transducers (5 to 20 MHz). The etalon is a block of aluminum in water. Since the acoustic impedance of aluminum is around 17 Mrayls, and that of water is 1.5 Mrayls, the reflection of each surface is ~ 85%. This will not be a high finesse etalon, but good enough to show the basic characteristics of such a device. The distance between the peak responses of the receiver Sound Head is the free spectral range of the etalon, and the width of the peaks gives the finesse. These two quantities can be compared to calculated values derived from the length of the etalon and the acoustic impedances.

Acoustical Etalon Equipment

Required:

  • two Sound Heads
  • a sweep generator or white noise generator
  • a spectrum analyzer

Accessories included in the kit:

  • material samples of aluminum and copper
  • a petri dish

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Literature

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Resources

Books and Articles

  1. B. A. Auld, Acoustic Fields and Waves in Solids, 2nd Edition, Krieger Pub. Co., 1990
  2. Experiments in Mechanics, Wave Motion and Heat, Laboratory Manual for 29:011, 29:027, & 29:081, Experiment W1: The Speed of Sound, Department of Physics and Astronomy, The University of Iowa
  3. A. R. Selfridge, Approximate Material Properties in Isotropic Materials, IEEE Transactions on Sonics and Ultrasonics, Vol. SU-32, No. 3, May 1985
  4. Korpel, A., Acousto-Optics, 2nd edition, 1997, Marcel Dekker, Inc.
  5. D. T. Pierce and R. L. Byer, Experiments on the Interaction of Light and Sound for the Advanced Laboratory, Am. J. Phys. 41, 314 (1973)
  6. R. Vogel, Optics Laboratory Extensions, Eur. J. Phys. 36 (2015) 055045

Web Sites

www.ndt-ed.org
This is the web site of the Non-Destructive Testing Resource Center. It has a large amount of instructional information on it. Follow the “NDT Instructional Material” link to the Ultrasound part.

www.ondacorp.com
Onda has a good reference section on their web site, including a large table of material properties.

www.physics.umd.edu/courses/Phys621/gradlab/glhb/acousto.html
This is the manual for the University of Maryland's acousto-optics advanced laboratory experiment.

physics.indiana.edu/~courses/p309/exp-procedure/31_Debye-Sears.pdf
This is the manual for the University of Indiana's acousto-optics advanced laboratory experiment.

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IOWA DOPPLER PRODUCTS
P.O. Box 2132
Iowa City, Iowa 52244 USA
Phone 319-359-2268
E-mail  idp@iowadoppler.com

Last updated May 27, 2017