The most important reason for good sound is that it is essential for good storytelling. Audio is very powerful and versatile for video, TV and film. Good quality audio and music encourage the audience to feel emotion and connect with the characters. Low budget video often neglects audio because the main focus is on the video quality. Many film makers prioritise audio before video.
Audio over video
There are two main elements to videos; picture and sound. Good audio quality is often a secondary factor for low budget video. Audio should be a primary factor. Many people overlook audio because video quality seems more important however, music and audio provides just as much entertainment for audiences.
Types of microphone for good audio quality
Dynamic microphones have three main parts. The diaphragm, voice coil and magnet. They have a simple design. The sound waves from the microphone cause a wire or coil to vibrate in a magnetic field that produces a current.
Condenser microphones also have three main parts. The diaphragm case, diaphragm, and the back plate. This microphone is a little more complex than the dynamic and can pick up a wider frequency response, plus a more natural sound. The condenser microphone can be useful background noise rejection.
Ribbon microphones – this microphone has a very natural sound. They actually fall into the dynamic category. This microphone got its name from having a long sheet of aluminium that is a primary function in this microphone. Not all of them are made with aluminium but most are. The thin peace of ribbon vibrates and is suspended into a magnetic field. It usually provides a warmer sound.
Polar patterns determine what area around the microphone picks up audio the best.
Cardioid – audio that is mainly picked up at the front of the microphone. If you were to speak and move around the 180 degree radius, the sound will start to drop off, cutting off higher frequencies picked up,Omnidirectional – is a microphone that picks up sound all the way around its 360-degree radius. The volume is consistent and there should be no drop offs.
Super cardioid – has a pick-up field that is narrower than a standard cardioid microphone. This means that there is more side rejection and recording with this microphone is more focused on the sounds coming out of the front. The downside is a slightly thinner sound.
Figure 8 – has a very unique polar pattern. The front and back of the microphone are the only areas that are sensitive to sound, hence the name because of the figure 8 shape.
Environment for good audio quality
Solid rooms will affect the way audio sounds.
Direct sound – doesn’t reflect and goes straight to the ears. The tone isn’t altered and frequency balance remains pure.
Reflective sound – we hear reflective sound later because it bounces off surfaces before it gets to our ears. In an average room, there is 6 surfaces that sound will hit before the ear. A disadvantage of reflective sound is the interference pattern it creates when it hits a surface. This changes the original sound wave.
Sound proofing – is used to decrease the level of sound travelling in and out of a room. Heavy building material can be used to insulate the room. You can also seal any gaps in the rooms and seal windows for extra sound proofing.
Acoustic treatment – is used to manage the reflections in a room to make sound recordings clearer. There are 3 things to consider to make your room sound better:
- Bass traps – are used to absorb low frequencies
- Diffusers – are used to disperse the remaining frequencies
- Acoustic panels – are used to absorb the mid/high frequencies
Cabling quality makes a difference. Having the right cables for your audio quality is important. Lets talk cables. Unbalanced cables – also known as instrument cables are used for instruments such as keyboards and guitars. Ideally these cables should be less than 25ft to reduce the risk of unwanted noise. Mixers are often longer than that so this is where the direct box comes in to it. The direct box converts an unbalanced signal to a balanced signal and sends it to the mixer without unwanted noise.
Positioning your microphone for good audio quality
In terms of close proximity, you don’t necessarily have to be close to be heard. Finding the right positioning for you and your microphone is key. For example, the Blue Yeti is a side address condenser microphone. This means that sound will only be picked up on the side of the microphone. Another example would be the SM7B which is an end address microphone. This means sound will only be picked up at the front end of the microphone. When you purchase your microphone, be sure to know which type you are purchasing and what polar pattern your microphone is.
A DAC is a digital to analog converter. This device converts a digital signal into an analog signal. This is then amplified and passed through a speaker. Signals from a digital domain can be stored on CD’S DVD’S and computer files etc however they aren’t useful to us unless they are converted back to analog. These signals are made up of ones and zeros known as a byte. These converters are useful because without them, we would see the digital signals that only electronic devices can read. Nowadays mobile phones etc have a DAC built in to convert the audio and music for crisp and clear sound.
It’s really important to monitor your audio. Headphones are great for listening to audio recordings as you can bring them everywhere as opposed to speakers. Monitoring will help detect unheard noises whilst on set that you may not have heard before.
Another reason for monitoring is to avoid something called digital clipping. Digital clipping is a crunchy noise that occurs when the sound on set gets louder than the pre-set audio levels. This can be an issue that could cost a significant amount of money to shoot again. If you try to fix the audio in post-production, it’s going to be a real challenge.
Good quality monitors are essential because they monitor your tracking, mixing and mastering which will ultimately contribute to the decisions you make. When choosing monitors, there are some things to consider. There are two broad categories of monitors:
Active – these monitors are what we work with mostly nowadays. They have everything built in already.
Passive – these monitors require an external power amplifier. It’s important to match the external amplifier with the monitors for the best quality.
Headphones are great for monitoring your audio.
- Cheaper than studio monitors
- Good to use when you have no acoustic treatment in your room
- Gives you privacy when mixing
- They sound the same everywhere on a bus, in the studio etc
- Great for editing tasks. You can listen out for clicks and pops. They can also help with setting reverb times because you’re locked in.
- The stereo can be too isolated from one to the other compared to minors.
- Having a different experience won’t necessarily get the same positive effect compared to using monitors.
- Wearing them for hours on end will make you fatigued. Sitting for long periods of time with them on may affect your working experience.
- Being in your own world isn’t always a good thing. Hearing other sound in your mix is essential for working efficiently. This may cause you to loose perspective on your mixing.
Tips on good audio quality
- Background noise- ensure that everything in your room is switched off if you can. Interference can affect the quality of audio. Anything like fans and air purifiers can be distracting to your audience.
- Use your polar pattern to your advantage – the polar pattern is located in your microphone. This tells you where the microphone picks up sound. For audio with spoken words, microphones with a cardioid polar pattern is often used.The reason for this is because the area around the microphone (excluding the front) doesn’t pick up too much sound. So, for any background noise it’s better to point the back of the microphone towards the air purifier for example. The cardioid polar pattern is 180 degrees so, anything at the rear will hardly be picked up when recording.
- Avoiding reverbs – a reverb occurs when sound bounces off hard surfaces. This is how echoes are created; especially in an untreated room. A good way to avoid this is to bring the microphone closer to your mouth. This will decrease the amount of reverb picked up.
- Avoiding plosives – a plosive is an abrupt sound that is realised and makes a kind of popping sound in the microphone. There are many types of plosives such as: P, T, B and D. For example, the word ‘pizza’ being spoken into a microphone is a consonant plosive.
A good way to avoid this is to move your microphone to the side of your mouth. Doing this will push the built-up air pass the microphones diaphragm. The distance should be 45 degrees to ensure the cardioid polar pattern will avoid these harsh pops of air whilst recording. Pop filters are another way to avoid plosives.
You might find this article on the feild of voice-over production interesting.