Its All About Sound! 1

By the end of this presentation you will: Understand the basic principles of sound measurement and its behaviour. Understand the Inverse Square Law. Understand and identify the various microphone pick up patterns available. Understand the requirement for correct microphone mounting and placement. Understand the requirement for correct headphones when recording sound. Objectives H20 Films -

When record good sound, a videographer must learn the nature of sound. Sound travels away from its source in a similar way to ripples caused by a stone thrown into a pool of water; the waves are larger at first and then fade out as they move away. The difference is that sound spreads in three dimensions away from its source. Nature of Sound H20 Films -

The speed of sound in air is approximately 1130 feet (344 meters) per second. The strength of these waves is called ‘amplitude’ and represents the distance from the peak to the trough of the wave. This roughly equates to volume or ‘loudness’. Nature of Sound H20 Films -

The rate of these waves is called ‘frequency’ and represents the time between peaks - the faster the peaks pass a given point, the higher the frequency. The human ear can discern frequencies within a limited spectrum; between 20Hz and 20kHz. In musical terms the range is something around 10 octaves Nature of Sound H20 Films -

Frequency is defined by the number of cycles it goes through in one second, originally this was known as ‘cycles per second’ (cps). The definition of wavelength is the distance a wave of a given frequency will travel in the time it takes for one cycle. Sound volume levels are measured in decibels (dB). Nature of Sound H20 Films -

The Inverse Square Law Sound intensity is a measurement of sound in Watts per unit area. As sound waves travel through air, each doubling of distance from a sound source results in a fourfold reduction of sound intensity. Nature of Sound H20 Films -

For example If you were to move away from a sound source in an area (with an absorbent ground surface) from 4 feet to 8 feet, the sound level is reduced by 6dB; another 8 feet to 16 feet the level is reduced by another 6dB (giving a total of 12dB); then move from 16 feet to 32 feet away, the total combined sound level reduction is 18dB, and so on. Nature of Sound H20 Films -

Location Shoots Take note of the environment. Listen, be aware what is happening around you. Microphones record or ‘catch’ everything without distinction. Get as close as you can to the source subject you are recording, and as far away as possible from any sound source that is producing unwelcome noise. Use headphones. Nature of Sound H20 Films -

Microphone is an instrument, or transducer, that changes one form of energy into another form of energy; in this case, sound waves into electrical signals. The quality of your recordings will vary according to the environment you are in. Elements such as the design of the microphone, its placement, ambient noise and weather will all have an effect. Microphones H20 Films -

Dynamic microphone are the most widely manufactured and used of all the types of microphone. They are a moving-coil design, which is simply a loudspeaker in reverse, and can be very durable and immensely cost effective. Condenser microphones works on an electrostatic principle rather than the electromagnetic principle employed in the Dynamic microphone. As a result it can produce an extremely high quality output. Microphones H20 Films -

Ribbon microphones are similar in some degree to their Dynamic cousins, but while they can produce excellent sound quality, they are sensitive to shock. Piezoelectric mics are traditionally strongly constructed utility microphones, but of poor sound quality. They are typically used in telephones. Microphones H20 Films -

Omni-directional microphones theoretically pick up sound equally in all directions. They are often used in Lavalier (tie-clip or lapel) mic systems. Microphones H20 Films -

Bi-directional microphones are used where there are two people involved in an interview; one on either side of the mic. Most ribbon microphones have this type of polar pattern. Microphones H20 Films -

Cardioid microphones are by far the most commonly used. It gets its name from its heart-shaped polar pattern. Microphones H20 Films -

The Super-cardioid microphone has a highly directional element that enables it to concentrate its ‘reach’ farther than its cardioid brother. Microphones H20 Films -

Hyper-cardioid microphone is similar to a cardioid microphone but with a closer area of front sensitivity and a much smaller area of rear sensitivity. Microphones H20 Films -

Shotgun microphones are the most highly directional of all the microphones and they are used to pick up sounds normally from longer distances, where it would be impossible to place any other microphone closer. Microphones H20 Films -

Parabolic microphones are specialised and they are often used in nature recording, and are very good at picking up birdsong. The parabolic microphone is a standard microphone with a built-on reflector dish that concentrates sound on to the capsule, similar to a satellite dish. Microphones H20 Films -

Microphone Mounting and Placement – how, what, why! (discussion point). Hand Held/Boom Stand-mounted Radio Microphones What Practical Applications? Microphones H20 Films -

Monitoring with Headphones Monitor your audio at the recording stage to ensure that you are indeed recording the sound you want, and to hear what your microphones are actually picking up. Your ears filter out unwanted sound but your microphones will record whatever they pick up. Headphones H20 Films -

Studio quality headphones provide a ‘neutral’ sound without tonal enhancements provided in hi-fi headphones. There will be less warmth and clarity added and the low and high frequencies will not be boosted. Noise cancelling headphones are of particular benefit to the audio recordist. Headphones H20 Films -

Headphones at too high a volume level can cause temporary or permanent hearing impairment or deafness. This often occurs unintentionally when filming in noisy environments. The sound recordist will naturally set the volume in the headphones at a higher level to compete with the background noise (a process known as ‘masking’) especially in excessively loud environments such as live concerts, roadsides, in large crowds and at wedding reception discos. Dangers of Hearing Damage H20 Films -

Three Stations: 1.Studio Environment Recording (voice overs) 2.Location Sound Recording 3.Reporter Interview Recording (vox pops) Practical Sessions H20 Films -