What is Sound?
- It is the range of frequency detectable by the ear (20Hz – 20KHz)
- Sound is a word that describes the brain’s perception and interpretation of a physical stimulus that is received by the ears.
Sound waves exist as variations of pressure in a medium such as air. It is created by the vibration of an object which causes the air surrounding it to vibrate. The vibrating air then causes the human eardrum to vibrate, which the brain interprets as sound.
Basic properties of sound
- Wave length – distance between respective thoughts or crest.
- Amplitude – strength or power of a wave signal (the light).
- Frequency – the number of cycles in one second.
- Period – the time it takes to make one cycle.
Characteristics of sound
- Refraction – it can change direction.
- Absorption – it can be absorbed
- Reflection – it can bounce back or off a surface.
- Diffraction – it can bend around an obstacle
In physics, sound is a form of energy known as “Acoustic Energy.”
Acoustics have to do with the transmission, reception, and clarity of sound within a given space. A given space refers to an enclosure.
You would have serious acoustic problems if the hall you are using has a lot of hard surfaces, if it is a vacuum, if it is not treated and if it is enclosed.
What is Audio?
Audio is the production, recording, manipulation and reproduction of sound waves. It can be said that sound and audio are of the same father and mother but sound is the junior brother to audio.
To understand audio, you must have a grasp of two things:
- Sound Waves: – what they are, how they are produced and how we hear them as explained earlier.
- Sound Equipment: – what the different components are, what they do, how to choose correct equipment and how to use them properly.
Some Field of Audio Work
The field of audio is vast, with many areas of specialty. Some common areas of audio work include:
- Studio sound engineer
- Live sound engineer
- Film/TV sound engineer
- Field sound engineer
- Post production audio creator etc.
The process of making a natural sound louder is referred to as amplification. This is where the original sound is insignificant in comparison with the amount of sound needed. Sound is made louder using an amplifying machine (amplifier) or what is called public address system (P.A.).
Amplify- this is the process of amplification
Uses of a Public Address System
- To provide adequate volume (not necessarily loud)
- To provide adequate clarity.
It is true that clarity makes the deference not just volume; that is why people often complain about not hearing the person speaking when what they actually mean is that they can’t clearly get what is being said.
Types of Public Address Venue
- The free field (open) – This is more of running an event in an outdoor venue. Here the engineer worries less about acoustics especially if there are no barriers at the venue and this is considered to be an ideal situation.
- The closed field (indoor) – This is an indoor venue. Here movement of sound waves can be disrupted.
Always ensure that nothing is in the line of sight of High Frequency drives.
This is because high frequencies have shorter wavelength. They are very directional. Low frequencies have longer wavelength so that they are omnidirectional.
Ensure the minimum account of reflection by pointing the speakers in a suitable direction.
When you set a sound, it is your duty as the engineer to identify the bad spots and you can solve them by speaker re-positioning and acoustic treatment.
This is another property of sound but a more advanced concept.
Here are some examples of how sound waves interact depending on their phase relationship.
- Sound waves which are exactly in phase come together to produce a stronger wave. Conversely, if the combinations of merging waves have the same polarity, addition will take place.
- Sound waves which are exactly inverted or 180 out of phase cancel each other out and produce silence.
- Sound waves which have varying phase relationship produce differing sound effect (distorted)
This is done using the ear.
The ear is a sensitive transducer that responds to this pressure variation by way of a series of related processes that occur within the auditory organs.
Sound is divided into consonants and vowels. Consonants have less power compared to vowels, so in a case of acoustic issue (reverberation time), the consonant sounds are affected since the vowel sounds have more power. Even though the consonants are more important to speech intelligibility.
The vowels having more energy bounce around the room longer, smearing and covering up the helpless consonants.
Our brain ear tends to average or smooth out different arrivals times of the identical signal up to 35ms (.035 sec) beyond that they are echo and echo lessens the listeners understanding another acoustic issue.