Sound

Interactive tutorial

The Decibel scale
This tutorial goes into the following: intensity of sound, inverse square law, logarithmic sound level and how to make calculations. This tutorial gives a summary of examination matter, and links to more detailed explanations of sound pressure and dB(A). It offers links to articles, exercises and a practical investigation about sound, and to a small tutorial about how to calculate with the decibel scale.

Beat
When two oscillations with slightly different frequencies are combined, a beat is originated: in the case of sound, you hear periodic variations in volume. Beat is used in tuning musical instruments. This tutorial explains how beats originate, and you can hear examples of beats.

Doppler effect
When you watch a car race on TV or in reality, you hear the pitch of the motor’s sound go down when it passes. A similar effect is heard when one passes a railway junction. And: what is meant when we say that an airplane breaks the sound barrier? This tutorial explains it with the help of animations.

Articles

Schiphol Airport: more transport with less noise.
An airport with a large network of connections is important for companies, employment and national economy. But it also creates costs in the form of stench, noise and increased risks of accidents. This article goes in the issue of noise. Linked sections go deeper into measurements and units of noise nuisance.

Sound and distance
In Amsterdam you can’t hear an airplane flying above Madrid, not even an airplane flying above Maastricht. This article explains how to use the inverse square law, the calculation rules for sound level and the effect of sound absorption. You will find a realistic formula, and with a Coach model you can calculate the effect of sound absorption.

Does sound of –5 dB exist? If so, can you hear it?
Is a negative sound level possible? Yes, and even though it is inaudible, there is an interesting side to its concept. Here, you can find out why we hear better at certain frequencies that at other. An animation will help you.

How does radar control work?
(This article appears to be favourite in Google searches!) Some people like to endanger themselves, other people and the environment by driving very fast. To catch those drivers, various techniques have been developed. Here we go into radar and lidar control.

Applications of the Doppler effect.
When, in 1845, the Dutch physicist Buys Ballot tested the theory of the Doppler effect, he wrote that it was interesting but without any practical use. Still, this effect like many other weird discoveries, turns out to have practical applications in the end.

Laser cooling.
A side step to a recent development, in which also the Doppler effect plays a role. Use powerful laser beams to cool down a gas to extremely low temperatures. How does that work? You can read it here.

Abnormal audibility I
The physicist Reynolds measured in 1876 that a normal cry (without megaphone) can be heard at a distance of at least 6.5 km. We now know that even at 9 km it is possible. You can download a Coach model here that shows you how this can happen, under certain circumstances.

Abnormal audibility II
Why do you hear an explosion at short distance, not at a larger distance and again at a much larger distance? You can download a Coach model that shows you how this is possible.

Hearing damage
About hearing damage, hearing aids and audiology.

Exercises

There are many exercises about sound. You can find them through the search menu, where you check the issue "geluid" (Sound). We specifically mention here the exercises for the tutorial on the Decibel scale and the exercise on laser cooling.

Practical investigations

Two examples of practical investigations on sound are the technical design tasks Dog whistle and Snoring detector.
Here again, ticking the box “geluid” in the search menu will help you. Some examples are Noise pollution near an airport, Voice recognition and Echography.

Studie en beroep

On this page you find examples of professions working with sound phenomena.