![]() ![]() If you have difficulty with only one or two of the questions you should follow the guidance given in the answers and read the relevant parts of the module. If you are sure that you can meet each of these achievements, try the Subsection 7.3Exit test. Study comment Can you answer the following Fast track questions? If you answer the questions successfully you need only glance through the module before looking at the Subsection 7.1Module summary and the Subsection 7.2Achievements. If not, proceed directly to the Subsection 1.3Ready to study? Subsection. If so, try the following Fast track questions. Study comment Having read the introduction you may feel that you are already familiar with the material covered by this module and that you do not need to study it. This final section also contains a few brief references to the nature of musical sounds. Finally, Section 6 shows how the superposition principle can be applied in the case of sound to account for such typical wave phenomena as interference and diffraction. It introduces the related concepts of intensity and intensity level and discusses the measurement of the latter in terms of decibels. Section 5 deals with the energy transported by sound waves. Section 4 concerns reflection and refraction of sound, and explains how these simple phenomena can be put to practical use in medical and other applications. ![]() Section 3 concerns the Doppler effect: the dependence of the observed frequency of a sound wave on the relative motion of the sound source and the observer. It also investigates the physical properties of a medium that determine the speed at which sound will propagate, and examines the way in which the properties of sound waves change as they travel from one medium to another. It explains what is meant by a longitudinal wave and lists the properties such as wavelength and frequency that may be used to characterize such a wave. Section 2 explores the nature and characteristics of sound waves. Hearing is a mental phenomenon, influenced by physiological and psychological factors that are still not fully understood, but sound is a purely physical phenomenon, and therefore a very suitable topic for a FLAP module. When the pressure waves arrive at the human ear they cause the vibration of various membranes and bones which in turn activate sensory organs inside the ear that send nerve impulses to the brain. It is these pressure waves that constitute the sound produced by the drum. The vibrations of the drum skin in Figure 1, for example, will cause the air above the drum to move back and forth, thus creating pressure waves that can travel through the surrounding air. The swish of the tyre and wind-noise contains a lot of high frequency energy, and you should find that this does not diffract around the corner as effectively as the rumble of engine.Sounds are made when objects vibrate. You can experiment with this by listening to traffic noise from a busy road from around the corner of a building (not in a direct line-of-sight to the traffic), and then moving to a location a similar distance from the road but in direct view of the passing cars. However with a short barrier (the same length as the wavelength) diffraction is very effective and there is almost no zone of silence behind it.įrom this, we can reach the conclusion that with sound waves, it is the low frequencies (which have long wavelengths) which diffract around corners. Our simulation shows that with a ‘long’ barrier, there’s a lot of reflection of incident energy back towards the source, but although there is some diffraction or bending of the wave around the barrier, this still leaves a zone of silence behind it. ![]() The obstacle in the right animation has the same width as the wavelength of the sound.īy examining the three animations, decide which of these statements is correct in the following quiz. Ripple tanks with large, medium and small objects (left to right) obstructing a wave. The key to understanding diffraction is understanding how the relative size of the object and the wavelength influence what goes on. Have a look at this a simulation of three ripple tanks, each containing an object of different width, which obstructs the propagation of a wave. ![]() Diffraction can be clearly demonstrated using water waves in a ripple tank. The amount of diffraction (spreading or bending of the wave) depends on the wavelength and the size of the object. Waves can spread in a rather unusual way when they reach the edge of an object – this is called diffraction. What is the reason for this? Do light and sound share any properties that might cause this effect? Diffraction Around An Object Have you ever wondered why you can hear someone who is round the corner of a building, long before you see them? It appears that sound can travel round corners and light cannot. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |