AUDIO Audio means "of sound" or "of the reproduction of sound". Specifically, it refers to the range of frequencies detectable by the human ear ﾑ approximately 20Hz to 20,000Hz. 20Hz is the lowest- pitched sound we can hear, 20,000Hz is the highest pitch we can hear. Audio work involves the production, recording, manipulation and reproduction of sound waves. To understand audio you must have a grasp of two things: 1. Sound Waves: What they are, how they are produced and how we hear them. 2. Sound Equipment: What the different components are, what they do, how to choose the correct equipment and use it properly. Understanding the basic path (signal flow) from the sound source through the sound equipment to the ear.

THE PRODUCTION PROCESS Pre-Production (Preparation) Tracking (Recording) Overdubbing Editing Mixing Mastering

What is SOUND?

Sound is a form of energy, just like electricity and light. Sound is made when air molecules vibrate and move in a pattern called waves, or sound waves. Sound waves exist as variations of pressure (compression & rarefaction) in a medium such as air. They are 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. Sound waves travel through air in much the same way as water waves travel through water. In fact, since water waves are easy to see and understand, they are often used as an analogy to illustrate how sound waves behave.

Perceived as Loudness Sound Pressure, levels, perceived loudness is measured in Decibels. Pitch, measured in Hertz, (the threshold of human hearing 20hz-20,000hz) Although sound waves are represented here in a two dimensional graph, sound when experienced in the real world is 3 dimensional. It has physical properties, you can feel the waves and they have the capacity to move through solids, liquids and gases. They also bounce off of physical objects creating echoes and when these echoes are reflected repeatedly off of surfaces in a room it is called reverberation (reverb.)

Unit of measurement used to perceive loudness in audio. 2 different kinds or applications (dB SPL and dB) The first application, dB SPL refers to your (sound pressure level)= the strength of sound. 0dB is how loud something has to be for us to hear it - the threshold of human hearing. It is important to understand that decibels are Logarithmic. This means that volume changes are not weighted on a 1:1 ratio, so when a sound goes up by three decibels it effectively is perceived as being twice as loud. We also use the decibel to measure the loudness of sound. The signal level or volume - turning up a few db or down a few db.

Phase is measured in degrees with 360 degrees being one complete cycle. Waves can be in phase, slightly out of phase (phase shift) or 180 degrees out of phase (phase interference.) or phase interference. The beginning of a wave is 0 degrees, the peak is 90 degrees, (one quarter cycle), the trough is 270 degrees and the end Is 360 degrees.

Harmonics A SINE WAVE is a pure tone of a single frequency like a signal from a tone generator. Most musical tones have a complex waveform which consists of more than one frequency component. All sounds are combinations of sine waves of different frequencies and amplitudes. The come together to form a complex sound wave. The lowest frequency in a complex wave is called the fundamental frequency. It determines the pitch of the sound. Higher frequencies in the complex wave are called OVERTONES OR UPPER PARTIALS. If the overtones are multiples of the fundamental they are called harmonics. If the fundamental is 200hz the second harmonic is 400hz, and the third is 600hz. Harmonics and their amplitudes play a large role in determining the tone quality or the TIMBRE of a sound. They help to identify the sound as a drum, piano, organ, voice, etc. Instruments with weak harmonics sound pure (flute), whereas, instruments with strong harmonics sound bright and edgy (trumpet, distorted guitar.) EQUALIZATION (EQ) can change the tonal balance of a recorded instrument by boosting or cutting its harmonics and fundamental frequencies. Boosting the fundamental tends to make the sound warm whereas cutting the fundamental makes it sound thin. Boosting harmonics makes the sound brighter, defined trebly, whereas cutting harmonics makes the sound dark or muffled.

Harmonics and Sound Waves Sine Wave (fundamental only.) Sawtooth Wave (fundamental and all harmonics.) Square Wave (odd harmonics only with varying degrees of amplitude.) Triangle Wave (odd harmonics only but they have weak amplitudes in comparison to the fundamental.) Even harmonics are more stable ratios such as octaves while odd harmonics are more unstable, like thirds and sevenths. Even and odd harmonics have different characteristics. Even harmonics are commonly referred to as being more stable, smoother, and comforting. Odd harmonics are usually described as more jarring, unstable, and sometimes harsh.

Envelope Attack (silence to max volume) Decay (max volume to mid-range) Sustain (how long the sound stays in the mid-range level) Release (sustain to silence)

Analog > Digital Conversion (ADC) Digital > Analog Conversion (DAC) An analog signal is a “real-world” signal. It is a steady stream of sound and can take on any value and can change continuously. A digital signal, on the other hand, is a stream of binary numbers ( ). To convert an analog signal into a digital signal, the analog signal must first be sampled, then quantized, and then encoded as a binary number. The signal is then in a form where it can be stored (like on a compact disk) or manipulated using the digital system techniques.

Analog to Digital Conversion converter Binary encoding o1o1o1o Converted to electrical signal or The converter measure samples (the voltage of the audio waveform) several thousand times per second! (Kind of like taking a picture of the sound.) Each time the waveform is measured, a binary number (01010) is generated that represents the voltage of the wave form at the instant it’s measured. This process is quantization. Each 0 and 1 is call a “bit” (binary digit). The more bits generated, the higher the bit depth and the more accurate the measurement and better the sound of the original sound wave.

Sample Rate and Bit Depth Low sample rate and bit depth vs. a higher sample rate and bit depth

Signal Characteristics of Audio Devices When a mic converts sound into electricity this it is called the signal. When the signal passes through an audio device - it may alter the signal. It might change the levels of some of the frequencies or might add unwanted sounds that weren’t in the original signal. Frequency Response for instance Microphones have various frequency responses - the way they respond to different frequencies - they may amplify low notes or bring out high notes- this is their frequency response. Noise Every audio component produced a little noise - you can make noise less audible by keeping the signal level in a device relatively high.If the level is low you have to turn up listening volume to hear the signal well thus increasing noise. Distortion If you turn a signal level up too high the signal will distort and your track will “clip”. Optimum Signal Level When the signal level is high enough to cover up the noise but low enough to avoid distortion. Signal to Noise Ratio The level difference between the signal level and the noise floor. The higher the S/N the cleaner the sound. Headroom The level difference between the normal signal level and distortion level is called “headroom.”

Types of Recording Live Stereo Recording (Portable 2 track recorder for on location stereo recording and field recording.) Live Mix Recording Computer Digital Audio Workstation (DAW) for home and studio recording. Stand Alone DAW MultiTrack recorder and mixer MIDI

Audio Equipment for Recording Microphones Phantom Power Supply Pre Amp Converter/Soundcard/Audio Interface often includes an onboard preamp.) DI Monitor System or Headphones Effects (hardware and/or software) Midi Equipment (Controller) Cables Mixer

MIDI (Musical Instrument Digital Interface) is a protocol designed for recording and playing back music on digital synthesizers (virtual instruments) that is supported by many makes of personal computer sound cards. Originally intended to control one keyboard from another, it was quickly adopted for the personal computer. Rather than representing musical sound directly, it transmits information about how music is produced. The command set includes note-ons, note-offs, key, velocity, pitch bend and other methods of controlling a synthesizer.