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## ultrasonic Quick reference

### A Dictionary of Construction, Surveying and Civil Engineering (2 ed.)

...Very high sound frequencies above the human audio range, which are about 20...

## oxygen Quick reference

### A Dictionary of Construction, Surveying and Civil Engineering (2 ed.)

...A gas at ambient temperature comprising 20% of the Earth’s...

## specific gravity Quick reference

### A Dictionary of Chemical Engineering

...specific gravity The ratio of the density of a substance to the density of water at 20 º C. The specific gravity of water at 20°C is therefore 1.0. ...

## audio spectrum Quick reference

### A Dictionary of Electronics and Electrical Engineering (5 ed.)

...spectrum The range of sound frequencies that are audible to the human ear. This is typically considered to be the range from 20 to 20 000 hertz , a span of eleven octaves . ...

## subsonic frequency Quick reference

### A Dictionary of Electronics and Electrical Engineering (5 ed.)

...frequency A frequency of value less than the lower limit of the human hearing range, i.e. frequencies below about 20 hertz. ...

## ultrasound Quick reference

### A Dictionary of Mechanical Engineering (2 ed.)

...ultrasound ( ultrasonic waves ) Inaudible sound waves, with frequencies greater than about 20 kHz up to many...

## reference temperature Quick reference

### A Dictionary of Mechanical Engineering (2 ed.)

...reference temperature (Unit K or °C) 1. In dimensional metrology, the reference temperature is 20°C. 2. See standard state...

## normal temperature and pressure Quick reference

### A Dictionary of Mechanical Engineering (2 ed.)

...normal temperature and pressure ( NTP ) Reference conditions defined by NIST as 20°C and 1 atm. See also standard state...

## low-temperature solar collector Quick reference

### A Dictionary of Mechanical Engineering (2 ed.)

...low-temperature solar collector A solar collector operating at temperatures a few degrees (maximum 20°C) above ambient. Swimming-pool heating is a typical...

## spectrum Quick reference

### A Dictionary of Electronics and Electrical Engineering (5 ed.)

...The range of possible frequencies that a particular (electrical) signal can have. For example, the audio spectrum is generally considered to extend from 20 hertz to 20 kilohertz, so a given audio signal will be found in this range, and a given instrument will have its own spectrum of frequencies or spectral response within this range. ...

## geometric mean Quick reference

### A Dictionary of Chemical Engineering

...geometric mean A type of mean value that is the average value of a set of n numbers, and calculated by multiplying them together, and extracting the nth root of the product. For example, the geometric mean of 10, 20, and 40 is and is less than the arithmetic mean, which is (10 + 20 + 40)/3 = 23.33. ...

## factorial Quick reference

### A Dictionary of Chemical Engineering

...factorial (Symbol !) The product of all the positive whole integers being considered. Note that 0! has a value of 1. For example, 5! is 0 × 1 × 2 × 3 × 4 × 5 = 20. ...

## schedule number Quick reference

### A Dictionary of Chemical Engineering

...schedule number A classification for pipes in terms of their wall thickness. There are ten schedule numbers in common usage: 10, 20, 30, 40, 60, 80, 100, 120, 140, and 160. ...

## primary air Quick reference

### A Dictionary of Mechanical Engineering (2 ed.)

...primary air In a combustor , the fraction (typically 15–20%) of the total air required for combustion which is introduced at the same time as the...

## Doppler ultrasonic flowmeter Quick reference

### A Dictionary of Mechanical Engineering (2 ed.)

...Doppler ultrasonic flowmeter A Doppler current meter where the frequency of the sound waves is in the ultrasonic region, i.e. above about 20 kHz. See also ultrasonic flow meter...

## sonicator Quick reference

### A Dictionary of Mechanical Engineering (2 ed.)

...sonicator A high-frequency ( c. 20 kHz) sound generator used to agitate liquids. Applications include ultrasonic cleaning , agitation of suspended particles, dispersion of nanoparticles , and...

## maximum allowable operating pressure Quick reference

### A Dictionary of Mechanical Engineering (2 ed.)

...maximum allowable operating pressure (Unit Pa) The highest pressure at which any pressure system may be operated, usually 10 to 20% below the maximum allowable working pressure...

## decibel Quick reference

### A Dictionary of Mechanical Engineering (2 ed.)

...( G ) A logarithmic measure of the ratio of two variables, V 1 and V 2 say, defined by G (dB) = 20log 10 ( V 1 / V 2 ). By choosing a suitable reference value for V 2 the decibel can be used as a measure of a variable V 1 , rather than of the ratio between variables. For example, sound pressure level ( SPL ) is expressed in decibel by SPL (dB) = 20log 10 ( p/p REF ) where p is the sound pressure and p REF a reference pressure, normally taken as 20 μ Pa. Because decibels are a logarithmic measure, they are additive when two variables expressed in...

## low-frequency oscillator Quick reference

### A Dictionary of Electronics and Electrical Engineering (5 ed.)

...oscillator ( LFO ) An oscillator found in musical synthesizers operating at frequencies up to approximately 20 hertz. It is used to modulate the fundamental frequency or amplitude of the output sound, referred to as ‘vibrato’ or ‘tremolo’ respectively. ...

## sound pressure level Quick reference

### A Dictionary of Electronics and Electrical Engineering (5 ed.)

...pressure level ( SPL ) The root-mean-square (r.m.s.) pressure of a sound wave at a particular instant ( P actual ), usually expressed in decibels (dBSPL) with respect to the average threshold of hearing at 1 kilohertz ( P ref ) of 20 micropascal: ...