Literaturnachweis - Detailanzeige
| Autor/inn/en | Allen, Thomas; Chally, Alex; Moser, Bradley; Widenhorn, Ralf |
|---|---|
| Titel | Sound Propagation, Reflection, and Its Relevance to Ultrasound Imaging |
| Quelle | In: Physics Teacher, 57 (2019) 3, S.134-137 (4 Seiten)Infoseite zur Zeitschrift
PDF als Volltext |
| Sprache | englisch |
| Dokumenttyp | gedruckt; online; Zeitschriftenaufsatz |
| ISSN | 0031-921X |
| Schlagwörter | Physics; Science Instruction; Acoustics; Diagnostic Tests; Audio Equipment; Laboratory Experiments; Teaching Methods; Computer Software; Visualization; Measurement |
| Abstract | The labs presented here build on a simple speed of sound activity and models medical ultrasound imaging by demonstrating how multiple reflections propagate in a closed system. A short sound pulse is emitted into a pipe that is closed at one end and contains one or more partially reflecting surfaces within the pipe. The variety of reflections and transmissions that occur can be measured with a microphone at the pipe entrance. We used white PVC pipes (4 m, schedule 40, 2-in diameter) and cut them into five pieces with lengths 0.4 m, 0.6 m, 0.8 m, 1 m, and 1.2 m (Fig. 1), cut to a precision of [plus-minus]1.6 mm. We connected the pipes with couplings and modified some couplings to cause partial reflections, by covering ¼, ½, or ¾ of the coupling opening. For easiest adoption, use repair coupling rather than a standard coupling. If standard couplings are used we recommend boring them out so that the pipes can easily be connected and disconnected. This activity requires a source to create a sound pulse as well as a receiver and logging/visualization software. A finger snap is the traditional source of sound, but some students struggle to produce consistently strong, short pulses. Sound editors with speakers, or even headphones, can provide this consistency. For instance, we implemented this activity in a teaching lab with multiple lab groups and had good results using Audacity to generate a tone in the 1000- to 4000-Hz range, a compact digital stereo amplifier (Lvpin 2020A+), and custom-made small speakers. For the results in this paper we used Audacity to generate a 1-ms tone at 2000 Hz, and headphones as a speaker. This pulse is short enough in duration to minimize the overlap of echoes in short pipes or pipes with multiple reflectors. Students can investigate how changing the pulse duration impacts the reflection data. Additionally, a sound editor that can produce a series of pulses will allow students to investigate the importance of selecting an appropriate pulse repetition rate. We used the commercially available Vernier microphone and Logger Pro data logging/visualization software to analyze the data obtained in the following experiments. The acquisition software was triggered to start recording when the sound pressure of the initial pulse exceeded a preset pressure level, which may vary depending on the sound source. We also set the sampling rate at 10,000 samples per second and the duration of recording at 0.1s. The pipes and couplings can be assembled a number of ways. Each pipe and coupling setup increases the complexity of the travel paths of the sound waves to mimic the reflection of ultrasound from internal body structures by allowing for reflections from multiple interfaces at different distances. (As Provided). |
| Anmerkungen | American Association of Physics Teachers. One Physics Ellipse, College Park, MD 20740. Tel: 301-209-3300; Fax: 301-209-0845; e-mail: pubs@aapt.org; Web site: http://aapt.scitation.org/journal/pte |
| Erfasst von | ERIC (Education Resources Information Center), Washington, DC |
| Update | 2020/1/01 |
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