At high frequency, when the wavelength is small compared to the object size, then the sound does not diffract very effectively. In acoustics, we use the term shadow zone to describe the area behind the object. Because if you stand there you are in an acoustic shadow (just like the […]
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. What is the reason for this? Do light and sound share any properties that might cause this […]
Superposition of Waves Superposition is a word used to describe what happens when one wave is superimposed – ‘sat on top of’ – another. To think about how two waves might add up, let’s start by looking at the peaks and troughs which we see whenever we encounter waves in reality. Using water waves as […]
The laws of reflection are the same for all types of waves, including light and sound. The video below shows light reflecting in a mirror. Laws of Reflection The angle of incidence is equal to the angle of reflection The incident ray, the reflected ray, and the normal all lie […]
At resonance the amount of energy lost due to damping is equal to the rate of energy supply from the driver. The driver is the source of external energy that keeps the oscillations going – for example, the person pushing a kid on a swing. Increasing the damping will reduce […]
If an oscillator is displaced and then released it will begin to vibrate. If no more external forces are applied to the system it is a free oscillator. If a force is continually or repeatedly applied to keep the oscillation going, it is a forced oscillator. Let’s use the example of a […]
Let’s go back to thinking about masses and springs. Imagine a mass held between two springs as shown in the animation below. If the mass is moved away from the equilibrium position the restoring forces provided by the springs will make the mass oscillate back and forth in a similar […]
Simple Harmonic Motion You may have heard the one about the opera singer breaking a wineglass with their voice. (In other versions it’s a greenhouse(?!), or even the specs worn by members of the audience). Well, if the singer could pull it off, they would be exploiting oscillations. Later, we’ll […]
Noise pollution is a big problem; it disturbing peoples sleep, increases risks of heart disease and harms learning in schools. If can also causes deafness. Case study: Noise Pollution at Glasto Even a great music festival like Glastonbury can cause noise problems for houses near the site. Acoustical Engineers have […]
The human ear is capable of hearing very quiet (low intensity) sounds and extremely loud (high intensity) sounds. The ratio of intensities between silence and ‘ow that hurts my ears’ is about 1:100 million million. It makes things easier if a logarithmic scale is used; this is what the decibel […]