Final Audio Engineering

Ground Loops

an unwanted electric current path in a circuit resulting in stray signals or interference, occurring, e.g., when two earthed points in the same circuit have different potentials.

Headroom

difference b/t peak and average signal. -operational range b/t normal and max levels -operational range b/t normal and max signal levels

Matching power rating w/ amplification

ex: a LS with a continuous power rating of 400 w will need an amplifier with 800-1,600w (2-4x more)

Masking

-Auditory masking occurs when the perception of one sound is affected by the presence of another sound. Auditory masking in the frequency domain is known as simultaneous masking, frequency masking or spectral masking. Auditory masking in the time domain is known as temporal masking or non-simultaneous masking.

Moving Coil Cone Driver

-Coil in magnetic field -current passes -2 Fields interact and cause movement -movement= cone -electrical to acoustic energy.

Series vs Parallel Wiring

-Components connected in series are connected along a single path, so the same current flows through all of the components. Components connected in parallel are connected, so the same voltage is applied to each component. -Parallel circuits are the simplest electrical circuit to wire. Parallel Speaker Wiring combines all Speakers (+) positive Speaker leads together, and all (-) negative Speaker leads together.

Mic Design Types

-Condenser, Moving Coil, and Ribbon

Equalizers (types, uses)

-Device used to adjust freq response. -Originally designed for signal loss. -make the sound equal. Uses: Clean, bring out certain Freq, compensate for the room, most common: correct losses or changes, enhance the sounds of instruments, reduce unwanted noises or leakage(Feedback, lower freq.) as and effect(talking on a cell phone) Types: -3 Band EQ -Parametric EQ: any freq in any range - 5 band parametric EQ: 5 knobs, lows: fixed frew on console, highs are fixed, the rest is covered in the midranges. -Sweep-able EQ: select different freq ranges, find range you are looking for. -to add more "brilliance" : shelving filter +3db @ 12kHz (high and low shelf) ****two types (not all) parametric and graphic****

Coaxial

-Drivers lack efficiency so we needed enclosures -Types: sealed or acoustic suspension and vented or ported.

Loudspeaker Enclosures

-Drivers lack efficiency so we needed enclosures -Types: sealed or acoustic suspension and vented or ported. -Vented loud speaker enclosures offer low freq extension, but boomy, less controlled bass.

Beats

-two tones that have different freq and have approximate amplitude. -because we can not perceive 2 separate sounds that are closely related

attenuation pad

-used to reduce gain on an incoming audio signal

Block Diagram

know how it works into block digram

Output sections

outputs the sound

Ohms Law

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. ... The above equation is the modern form of Ohm's law. In physics, the term Ohm's law is also used to refer to various generalizations of the law originally formulated by Ohm. Calculate: Ohm's Law and Impedance. ... The simple formula known as ohms Law that we all learned at school takes the form: R = V/I, where R is resistance (in ohms), V is the voltage across the circuit, and I is the current (in amps) flowing through the circuit.

Analog Consoles

relating to or using signals or information represented by a continuously variable physical quantity such as spatial position or voltage.

Refraction

Refraction of waves involves a change in the direction of waves as they pass from one medium to another. Refraction, or bending of the path of the waves, is accompanied by a change in speed and wavelength of the waves.

Mic vs Line level

Mic level is the lowest, or weakest, level signal of the four and requires a preamplifier to bring it up to Line level. Instrument level signals live between mic and line level signals and have the most variation. You typically see this kind of signal come from an electric guitar or bass.

Calculate wavelength of any frequency

Wavelength is represented with the Greek letter lambda: λ. Wavelength is expressed in units of feet. Speed of sound divided by Freq********** ex: 400 Hz sine wave 1130/400 = 2.825 Ft.

Decibel

unit used to measure the intensity of a sound or the power level of an electrical signal by comparing it with a given level on a logarithmic scale. -a measurement of loudness

Gain structure

Gain Structure is the term we use for the collection of various gain adjustments throughout the system - the mic preamp, the fader, the main mix output level, the input gain of a power amplifier or recorder, and so on. -The relative levels of the signal as it moves from the source to the destination

Grounding

Grounding In electrical engineering, ground or earth is the reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the Earth. -preventative measure because if there is a surge in the electrical circuit, that current is gonna want to find a path to the ground. -electrical stander-eds req that we have a 3rd prong on an outlet so if there is a surge in the outlet, it goes straight to a rod that is in the ground.

Limiter

***10:1 or greater ratio/ (10dB over thresh, only 1dB comes out)(difference b/t a compressor and a limiter) Uses: protects devices from overloading/distorting. ex: tape machine -live sound protects power amps -heavily compression makes sound sound differently -use it anytime you want to make sure the signal doesn't go past that level.

Unity Gain

- relative levels as it moves from the source to the destination. -be mindful because of everything will have an output level. -the state where a circuit outputs the same level it receives as its input

Speed of Sound

-1130 Feet per second - 1 Ft. per millisecond

Reverb

-A series of delays -simulation of sound in an acoustical environment -too many reflections, cant hear the individual delays. Types: hall, chamber, plate, room, reverse, gated. Reverb parameters: -Pre-delay: delay that happens b/f the reverb is heard. -diffusion: controls the space b/t the reflections -Decay time: the time it takes for the reverb to go away -Density: adjust the original short delay times. How thick it is. Uses: -sense of depth and believably -How far the singer is from you - Draws attention/ emphasis

Proximity Effect

-As the mic gets closer to the source, the low freq increases in relation to the high freq. -Proximity effect is a change in the frequency response of a microphone, having a directional pickup pattern, that produces an emphasis on lower frequencies.

Phase

-Audio waveforms are cyclical; that is, they proceed through regular cycles or repetitions. Phase is defined as how far along its cycle a given waveform is. The measurement of phase is given in degrees, with 360 degrees being one complete cycle.

Speech Intelligibility

-In speech communication, intelligibility is a measure of how comprehensible speech is in given conditions. Intelligibility is affected by the quality of the speech signal, the type and level of background noise, reverberation, and, for speech over communication devices, the properties of the communication system. ** speaking in the microphone** Rules: -Level should be b/t 60-70 dB (normal conversation) - 25 dB over the signal to noise ratio - less that 1.5 sec reverb -Achieve uniform coverage -Spectral integrity: things sound like they are so-post to .

4 questions to evaluate a sound system

-Loud enough?: level or SPL -Will it feedback?: regards gain structure -Can everyone understand?: Signal to noise(15 dB over competing sounds) or System intelligibility\ -Provides appropriate coverage? : Refers to the listening area (want it to be + or - 3 dB) -Does it sound good? : EQ, distortion?

EQ filter curves

-Peak: adding gain -Dip: reducing intensity -Notch: narrow cut just on a specific freq.

Haas Effect

-The Haas effect or the Precedence Effect is a Psychoacoustic Effect described by Helmut Haas as the ability of our ears to localize sounds coming from anywhere around us. -ability to locate a sound in space. -localize sound.

Critical distance

-The directs sound is at the same level as the reverberate sound. -(if too reverberate) either change your seating to get ppl closer to the speakers or put more speakers.

Off Axis Coloration

-dull or colored effect on sound sources that are not placed within the acceptance angle placed directly in front of the microphone. To avoid off-axis coloration, place mics so that they are aimed at sound sources that put out high frequencies, such as cymbals, when miking a large source. -Move off axis: Freq response changes(gonna sound different -Do not deviate from on axis.

Best way to hook up an FX unit

-hook it up as an aux sends so the effect can be mixed in.

Attack

-how fast the compressor is compressing

release

-how fast the compressor will go away

Aux sends

-pre fader: independent of the channel fader -post fader: dependent of the channel fader

Signal Processors (3 Types)

-processes our signal 1. Spectral processing: EQ 2. Dynamic processing: compressors, limiters, and gates. 3. Temporal: Reverb, Delay, chorus

Noise Gate

-provides an attenuation until the threshold is reached Uses: guitar amp, reduce unwanted sounds, as an effect, shut off the mic when it is not being used.

Horn Compression Driver

-same as moving coil but it is attached to a horn to increase its efficiency

Wireless microphone systems

1. transmitter 2. receiver 3. laviler/handheld/instrument **it is ok to have two different types of antennas on a wireless system**

3 to 1 rule

3:1 Rule of Microphone Placement. When using two microphones to record a source, normally you will get the best results by placing the second mic three times the distance from the first mic that the first mic is from the source. This is known as the "3:1 Rule of Microphone Placement." -Distance b/t mics= 3x the distance from the Mics intended source. -Important to eliminate phase problems

Speaker Impedance

4-ohm Speakers Should Typically Be Mated with Higher Power Amplifiers. Most bookshelf and tower speakers are rated either 6-ohms or 8-ohms. Any speaker impedance rating that is 4-ohms is typically going to be a high-end, audiophile product that wants an amplifier that can really put out some power. ex: how many 8 ohm LS will be needed to create a 4 ohm load on one channel of amplification? 2 because its the impedance of the loud speaker times the number of speakers needed

Crossover Networks

A crossover is an electronics device that takes a single input signal and creates two or three output signals consisting of separated bands of high-, mid-, and low-range frequencies. The different bands of frequencies feed the different speakers, or "drivers," in a sound system: tweeters, woofers, and subwoofers. -a cross over splits into freq bands and sends freq to an appropriate driver. **the type of crossover that is found inside an enclosure is passive**

loudspeaker arrays

A line array is a loudspeaker system that is made up of a number of usually identical loudspeaker elements mounted in a line and fed in phase, to create a near-line source of sound.

Microphone Directional Patterns

A microphone's polar pattern is the 3-dimensional space surrounding the capsule where it is MOST sensitive to sound. The 3 basic patterns are: omnidirectional figure-8 cardioid

Absorption

Acoustic absorption refers to the process by which a material, structure, or object takes in sound energy when sound waves are encountered, as opposed to reflecting the energy. Part of the absorbed energy is transformed into heat and part is transmitted through the absorbing body.

active vs passive splitters

Active is preferred over passive because there is no signal loss as opposed to passive where you have a loss of 3db signal everything it is split.

Signal routing

An audio router is a device that transports audio signals from inputs to outputs.

Diversity

Antenna diversity, also known as space diversity or spatial diversity, is any one of several wireless diversity schemes that uses two or more antennas to improve the quality and reliability of a wireless link. -diversity has two antennas to pick up a signal, it is preferred because if the signal on one source is dropped, it has another antenna to pick it up.

Balanced vs unbalanced

Balanced: Balanced audio is a method of interconnecting audio equipment using balanced lines. This type of connection is very important in sound recording and production because it allows the use of long cables while reducing susceptibility to external noise caused by electromagnetic interference. Unbalanced the ground wire still surrounds the signal wires and is used as a shield against interference. Balanced Vs unbalanced A balanced cable, by contrast, has three conductors in the connector and three wires in the cable: two signals wires plus a separate ground wire. As in the unbalanced cable, the ground wire still surrounds the signal wires and is used as a shield against interference. ... Balanced signals are what is called differential.

Compressor (uses, likely controls)

Compresses the audio signal -reduce the dynamic range as the signal increases. -often gain make up gain is added and raises levels of lower level sounds (bellow the compression threshold) Controls: threshold(where are you starting the compression) , compression ratio(sets the amount gain level of reduction. the degree where the dynamic range is reduced), attack(how fast the compressor starts compressing) , release(how long does it take for the compressor to restore the level) , outputs(makes up for gain reduction). Uses: Vocalist, drums, guitarist, sound effects -control/manage/reduce dynamics (bring up low level sounds) -increase or decrease the initial attack. -Voice over mixing-key import the voice track reduces the level of the music track. -de-esser: uses an EQ during a silibant sound, compresses by freq. ****As an insert because it is added as apart of the signal chain**** -The ratio is dependent on the amount of signal going out after going over the threshold ex:2:1, for every 2db over threshold. 1 comes out.

Directivity of Sounds

Directivity is a measure of the directional characteristic of a sound source. Direct sounds: arrive within 0-25 ms. 25ft away(different sounds than direct) Early refection - 25-100 ms Even further away(Different sounds than early reflection) Reverberation- anything greater than 100 ms

Transducer

Definition: A transducer is a device that converts one form of energy - typically a signal - into another. Pronunciation: trans•dyoo•ser. Example: A speaker is a type of transducer that converts electrical energy (the audio signal) into mechanical energy (vibration of the speaker cone/diaphragm). -Any device that transforms one type of energy into another type of energy. -ex: Ear -Types: Magnetic induction transducers, and Variable Capacitance. ex: Mic capsule(A condenser or capacitor microphone is basically a stretched conductive membrane suspended above a fixed conductive plate. This membrane and backplate ("the capsule") are the two key components that define the mic as a "condenser".) begins the flow of electrons.

Calculating Impedance

If all the speakers in parallel have the same impedance, then the calculation is easy. Simply divide the impedance by the number of speakers in parallel. Example 1: Four 8 ohm speakers in parallel: 8 divided by 4 = 2 ohms. Example 2: Two 4 ohms speakers in parallel: 4 divided by 2 = 2 ohms.

Direct vs Alternating Current

In direct current (DC), the electric charge (current) only flows in one direction. Electric charge in alternating current (AC), on the other hand, changes direction periodically. The voltage in AC circuits also periodically reverses because the current changes direction.

Signal Flow

Know how delay moves into signal flow

Three categories of communication

Public announcement: generally said to everyone Direct public address: specifically said to someone. ex: Sermon Performance: Theater, Any live event.

Reflection

Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves.

Signal Flow

Signal flow is the path that the audio signal takes from the input to the output in an audio console. The signal first enters the console through an input. An input is usually a balanced signal that enters at mic level.

Inverse square law

The Inverse Square Law teaches us that for every doubling of the distance from the sound source in a free field situation, the sound intensity will diminish by 6 decibels. ... The intensity of the sound is inversely proportional to the square of the distance of the wave front from the signal source. -Sound falls off according to the square of the distance. -ex: Moving away from a speaker. -Doubling the distance from the sources is a loss of 6dBspl (Doesn't include room reflections) -**When you double the distance from the source SP goes down by 6dB -double the distance from the source, you loose 6 dB. important for uniform coverage. -Add more speakers when loosing sound SPL

Hertz

The hertz (symbol Hz) is the unit of frequency in the International System of Units (SI) and is defined as one cycle per second. It is named for Heinrich Rudolf Hertz, the first person to provide conclusive proof of the existence of electromagnetic waves.

Loudspeaker coverage

The radiation pattern of the loud speaker is defined by the angle facing away from the front of the speaker and 6db.

Polarity

The use of the term 'flipping the phase' or 'inverting the phase' is a common misnomer that I see time and time again by professional and amateur alike. The problem is that to invert the phase of an electrical signal simply does not make sense, and what is most commonly meant is actually a polarity inversion. -the relative orientation of poles; the direction of a magnetic or electric field.

Input sections

This is the section where audio signals from microphones and/or playback equipment enters the mixer This is the area where impedance matching and Balanced / Un-balanced lines must be carefully watched The input buss**two signals are properly combined** typically starts at the rear of the console with either XLR or ¼" TRS connectors -preamp , eq, aux, signal routing ( 1&2, 3&4 (assigns it to output, and the mute button) -Phantom Power -Mute Button -Polarity Reverse -Channel Fader Insert -Allows you to insert a signal processor in the signal path of that specific channel. High Pass Filter (HPF) -Lets high frequencies pass through unaffected but cuts the low frequencies. -Either fixed (80Hz) or Sweepable (<200Hz)

Matching amp to speaker

This means a speaker with a "nominal impedance" of 8 ohms and a program power rating of 350 watts will require an amplifier that can produce 700 watts into an 8-ohm load. For a stereo pair of speakers, the amplifier should be rated at 700 watts per channel into 8 ohms.

Squelch

a circuit that suppresses the output of a radio receiver if the signal strength falls below a certain level.

Circuits

a complete and closed path around which a circulating electric current can flow.

Block Diagram

a diagram showing in schematic form the general arrangement of parts or components of a complex system or process, such as an industrial apparatus or an electronic circuit.

Delay

repeat of signal -aka echo -waits before sound is heard -slap-back delay: simplistic form(80ms with a single repeat) -Feedback= #of repeats -delay times: in time w/ music Why use it? -gives perception we are listening to bigger than what it is. -combine original sound, harmonics of each -pitch discrepancies average out -use it as an effect to create an even larger space.

Gain Before Feedback

the amount you can increase the gain level b/f it starts to send feedback

Impedance

the effective resistance of an electric circuit or component to alternating current, arising from the combined effects of ohmic resistance and reactance. Impedance in audio On the output side, a loudspeaker may still have a nominal impedance of something like 8 ohms, which formerly would have required having an amplifier output stage carefully matched to 8 ohms. But now with the active output circuitry of audio amplifiers, the effective output impedance may be very low.

Diffraction

the process by which a beam of light or other system of waves is spread out as a result of passing through a narrow aperture or across an edge, typically accompanied by interference between the wave forms produced.