Experiences

Acoustic

Mária Fabianová

Slovakia

Lower Secondary School

Chemistry

Teaching in class

Direct

Acoustics is discussed in the topic of oscillation and waves. Students already know what it is oscillation and they can describe undulation. Not each oscillation is also undulation but each undulation is oscillation.
Acoustics deals with the sound as a mechanical undulation which is spread in flexible environment. From the lessons when we talked about the matter, they already know that there is about 70 kg of air in the classroom and this is that flexible environment which enables that sound is spread and we can talk to each other. For the whole day we live with sounds. There exists some sound background about which we sometimes even did not think. People who lost their hearing lost also their orientation in the space, they feel threatened because information about surroundings are gained not only by vision but also by hearing.
Sound is spread in solid, liquid and also in gaseous substances. In solid substances it is spread faster as in the air, for example we will notice the train through the rails than through the air. Even now this experiment sounds funny to students.
Acoustics deals with the generation, propagation and perception of sound. The speed of sound depends on temperature, it increases with the temperature. When numeric tasks are solved the speed of sound is considered to be about 300 to 330 m/s.
Our detector of sound is ear. Its shape is not random. If we lost outer ear we would not hear. Hearing centre is in our brain, this centre sorts sounds and therefore we perceive some sounds as pleasant and some as unpleasant.
In nature everything has its plan and purpose. Some animals have in comparison with their body size big outer ear. It is not only for sensitivity of sound but they have also cooling function because blood which flows through this space is getting colder.
Sounds are divided into musical and non-musical. Musical sounds are called tones and are generated by periodic oscillation of the source. Non-musical sounds are everywhere around us – banging, creaking … they are generated by irregular oscillation of the source of sound.
In human speech vowels are tones and consonants are non-musical sounds. Unit of the sound intensity is B (bell) but also smaller unit is used – dB. It is named after Graham Bell who invented the principle of telephone.
Then we compare beginnings of telephoning, we compare automatic phone exchanges and it was needed to wait for a phone call for hours with nowadays way of phoning. Today’s technology has changed human life, mainly the way of communication, which is many times limited to a brief text messages. The notepaper is not being sold anymore and I think that it is the negative influence of the technique.
There exists threshold of hearing. It is the lowest sound intensity that a human is able to hear. This intensity changes with age and elderly people have this threshold at higher level. Then there is also threshold of pain when we perceive the sound as a pain.
Long-term stay of human in noisy environment influences the whole organism, from headaches to total collapse of organism.
Very long conversation about today’s music follows. Each generation of people has its own music at this age. Many of them have never heard the name Mozart, some of them roughly remember that Beatles existed… then they ask me what music I like listening.
I consider this experience to be positive.