Audio Engineering

Decibel

a 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

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.

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.

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.

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

Variable capacitance

-Electrostatic operated

Beats

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

Calculate Ohms law

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.

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.

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.

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.

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 wave

Wavelength is represented with the Greek letter lambda: λ. It is equal to the velocity of the wave, divided by the frequency. Wavelength is expressed in units of feet

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.

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.

Moving Coil Mic

-Magnetic -A type of mic in which incident sound waves strike a diaphragm, which is connected to a moving coil, the coil moves within a constant magnetic field which produces the output signal. -Also called Dynamic -Most useful in the Studio -Most durable -Close up applications -Can not withstand allot of sound pressure -works well with vocals

Ribbon Mic

-Magnetic -Fragile -No power Source Req.

Magnetic Induction

-Metal with a Magnetic -ex: Moving Coil+Ribbon -Dynamic Mics

Condenser Mic

-Most Sensitive -Based on Variable Capacitance -Uses a Capacitor to convert acoustical energy into electrical energy.

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.

3:1 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.

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.

Microphone Directional Pattern

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.

Directivity of Sounds

Directivity is a measure of the directional characteristic of a sound source.

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.

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.

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.

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.

Omni-Directional

In every direction, especially of an antenna capable of transmitting or receiving signals in all directions, or of a microphone capable of detecting sound from all directions

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

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.

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.

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.

Impedance

the effective resistance of an electric circuit or component to alternating current, arising from the combined effects of ohmic resistance and reactance.

Unbalanced

the ground wire still surrounds the signal wires and is used as a shield against interference.

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.