This week, we revisited audio, how we hear sound, and the types of microphones together with there uses. We ended the week by creating 2 audio projects that entailed everything that we had learned. The first thing we did was learn exactly how audio travels through the air to the ear of the listener, and what determines the level at which it is heard.
Sound travels through waves, and there are 2 types; transverse waves and longitudinal waves.
Sound is a wave of vibrations through the air. In order to form a wave, the sound needs a medium to travel through. A Transverse wave is created when the medium is vertical to direction of the wave. This can be seen in the first illustration above. Examples of how they can be visualized is the ripple of a pond or a wave on a string. Generally, transverse waves occur on the surface of a liquid, on a string or through a solid. They cannot occur in a liquid or gas as there is no way that the displacement is in a vertical or perpendicular direction to the wave.
In Longitudinal Waves, the direction of the medium is instead parallel to the wave, which forms in a ‘slinky’ like motion which can be seen in the second illustration above.These sound waves can therefore travel through air and water.
When sound is travelling through a medium in the form of a wave, the sound is vibrating in a back and forth motion. The rate at which it is vibrating is called its frequency. The frequency of a wave describes the amount of times the particles of the medium vibrate when a wave passes through it. A waves frequency can be measured by the number of vibrations of a particle per unit of time. For example, if a particle vibrates 3000 times in 3 seconds, its frequency will be 1000 vibrations per second.
Amplitude is defined as the maximum displacement of points on a wave. It is the intensity of change within a wave, and in regards to sound, it measures the change in it’s levels (the volume). It can be measured vertically from the peak of a wave to the equilibrium position.
For out first practical task for the week, we tested different types of microphones, and how they sound in different environments. It can be heard here : week-5-audio-task-pp
The types of microphones we used and tested were
- Shotgun microphone
- Lavier microphone
- Dynamic microphone
Shot gun microphones
A shotgun microphone is long and pointed in shape, and is highly directional, meaning that it picks up most of it’s sound at the very tip. It has a unidirectional polar pattern, and must be pointed directly at the source of sound. When positioned like this, it picks up the main source of sound with a very high gain, while recording other noises that are present very subtly. It is able to illuminate background noise while still recording quality sound where it is directed. A shotgun microphone is often used for speeches at conferences, lectures and meetings. It is particularly beneficial when the subject speaking is in close enough proximity to the camera so that a boom stick can be held at a distance with the shotgun attached at the top. This way, the desired sound can be picked up effectively without the microphone being in shot of the filming.
Lavalier microphones are used most commonly for a hands free option. It is a small microphone which picks up sound in one direction only, and can be attached to the subjects clothing. It is therefore ideal for interviews. There are two pieces to this microphone- a transmitter and a receiver. If the transmitter is wireless, it can be attached to the lower clothing of the subject, for example, their waist, while the actual clothing will be attached somewhere between the throat and chest. If the transmitter is connected to the receiver by a wire however, it will be a bit more tricky to conceal it completely. However, it does cost a lot less money than a wireless one, and works just as well.
The Dynamic Microphone is great for general use and is extremely versatile. The build of the microphone is simple and very sturdy so that it can withstand rough handling and moisture. They do not require an external power source and are ideal for handling high volume levels, for example at a music concert or large presentation. As they are omnidirectional, they pick up sound solely from one direction, and have to be pointed directly at the source of desired sound. They work when the diaphragm is hit by a sound wave causing it to vibrate.
Evaluation of Microphone task
Shotgun in quiet corridor : in this recording, the voice is extremely clear with minimal to now background noise. It is also significantly louder than the other recordings, and this may not only be due to the shotguns known benefits of picking up sound in the direction it is pointed well, but also can have something to do with how close the microphone was held to the speakers mouth.
Lavalier Microphone in quiet corridor: Although a person who is speaking in the background is very loud and quite clear, the lack of white noise in comparison to the shotgun recording is noticeable. This is because the microphone is picking up sound from one direction only. It is not as loud as the previous recording however, and this can be due to the position of the microphone and how close or far away it was from the speakers mouth.
Dynamic Microphone in quiet corridor: The sound quality for this is quite similar to that of the shotgun. Although the speakers voice is loud and clear, there is a slightly more muffled sound in the background than the lavalier recording.
Shotgun microphone in a outside environment: In this recording the background noise of people chatting is clearly noticeable. However it does not interfere with the clarity and levels of the speaker talking. It is ideal for an interview or documentary, where the speaker needs to be heard clearly in a busy environment, but an essence of the location and what is occurring around them is still notice in a subtle way.
Lavalier microphone in an outside environment: In this recording, the background noise of the hustle and bustle outside is significantly quieter. It is still slightly noticeable, but definitely not to the same extent as the shotgun microphone.
Dynamic Microphone in an outside environment: In this recording, this is actually little to no background noise that is noticeable at all. The speakers voice is the only focus. Although the microphone is omnidirectional, the fact that it is significantly quieter than the background noise in the lavalier microphone recording (which is also omnidirectional) can also be due to the fact that it was recorded in a more quiet space, or at a time where there was not a lot of noise around.
Shotgun Microphone, Lavalier microphone and dynamic microphone in an inside open space: For the open space location, I grouped all of the microphones together as the results from the recording are not a lot different to what was previously said about each microphone. The shotgun picks up the speakers voice clearly, but with background noise and the lavalier microphone and the dynamic microphone both eliminate background noise as the are very directional, with the lavalier microphone having a slightly clearer recording of the speakers voice. One very noticeable difference with all of the clips in this location however, is the echo of the speakers voice which was not present in any of the other locations. This is definitely due to the fact that the open space where it was recorded had a particularly high ceiling, and was of course very spacious.
I’d first like to highlight from the video above that the editing is quite terrible, with the text being inconsistent. Also, not very much thought was put into the actual answers to the interview questions and I realise that they could have been a lot better and a bit more intellectual. However, as the main focus on this task was microphones and their uses, I will focus on this.
Social Media Report