A short EDT is a good indicator of speech clarity, as early reflections that reach the listener within 50 milliseconds integrate with the direct sound and can improve speech clarity - see the Haas effect.

See also backward curve integrationEAV (exposure action value)

**Echo Definition IEC 801-31-21,** sound wave that has been reflected and arrives with such a magnitude and time interval after the direct sound as to be distinguishable as a repetition of it.

EDT (early decay time)

The *effective level* is also known as the average level and the effective value.

**Effective Perceived Noise Level Definition IEC 801-29-15,** level in decibels of the time integral of the antilogarithm of one-tenth of the tone-corrected perceived noise level, over the duration of an aircraft flyover; the reference duration is 10 s.

● Note 1 : the integral is usually approximated by one-half the summation, over the top ten decibels of an aircraft flyover, of the antilogarithms of one-tenth of the tone-corrected perceived noise level in successive 0,5 s intervals.

● Note 2 : Effective perceived noise level purports to represent subjective noisiness.

● Note 3 : Effective perceived noise level of an aircraft flyover tends to be 2 dB or 3 dB greater than A-weighted sound exposure level.

See also, judged perceived noise level • maximum perceived noise level • noise exposure forecast • noise and number index • perceived noise level • tone-corrected perceived noise level

Effective Sound Intensity

Effective Sound Pressure

See also, effective level • RMS (root-mean-square) value

**Because of their importance in acoustics, we include more details, see measurement microphones**

See also propagation loss • sound propagation

ELV (exposure limit value)

**Energy Level Definition IEC 113-06-01,** for a system of particles and fields, set of states associated with a specified energy

● Note 1 : this concept is particularly useful when energy changes by quanta.

● Note 2 : the term *energy level* is also used for the associated energy.

*Energy-average Sound Pressure Level in a room*, under sound insulation

See also sound energy density

In the case of

In the case of *total rate of energy transfer*, the SI unit is the Watt (W).

See also other types of averaging

**Environmental Noise (UK Regulations)**

aircraft noise •
industrial and port noise •
railway noise •
road traffic noise

EPNdB (effective perceived noise level)

EPNL (effective perceived noise level)

**
Equal Loudness Contour Definition IEC 801-29-08,** curve that shows, as a function of frequency, the sound pressure level required to cause a given loudness for a listener having normal hearing, when listening to a specified kind of sound in a specified manner.

A stable situation in which all the forces cancel on another.

Equivalent Acceleration (Aeq, Aeq4, Aeq8)

**Equivalent Continuous Sound Level Definition** IEC 801-22-16, logarithm of the ratio of a given time-mean-square, standard-frequency-weighted sound pressure for a stated time period, to the square of the reference sound pressure of 20 μPa. *Time-average sound level* in decibels is 10 times the logarithm to the base ten of that ratio, also known as the time-averaged sound level and the *LAeq*.

● Note 2 : in principle, exponential time weighting is not involved.

**Equivalent Continuous Sound Pressure Level Definition** IEC 801-22-11, logarithm of the ratio of a given root-mean-square sound pressure, during a stated time interval, to the reference sound pressure. Average sound pressure level in decibels is 20 times the logarithm to the base ten of that ratio and is also known as the time-average sound pressure level

Note the fundamental differences between these two definitions

Equivalent Sound Absorption Area

**Erg** the amount of work done by a force of one Dyne exerted for a distance of one centimetre.

In the CGS base units. 1 erg = 1 dyne cm = 10^{-7} Joule

ESD (energy spectral density)

Estimated Noise Dose.

Estimated Vibration Dose Value

EU (engineering units)

eVDV (estimated vibration dose value)

Evening Noise Indicator

See also day noise level • day evening night noise level • night noise level.

Every time the sound energy doubles the measured dB level increases by 3 dB, i.e. the *exchange rate Q = 3*. For example if a machine produces 80 dBA then adding another identical machine increases the measured level to 83 dBA. So four identical machines, 4 times the sound energy, would measure 86 dBA, we are adding decibels not numbers. This is explained in detail with examples in our sound level calculations article.

Sound Exposure and Noise Dose follow the same rule - a doubling of the level results in a 3 dB increase. However they are also both time dependent. So if the exposure time is doubled the total sound exposure increases by 3dB. Similarly if the noise dose was 100% of the acceptable daily maximum, then doubling the exposure time results in a total noise dose of 200%, twice the daily limit.

Leq in the UK, Europe and many other places is also based on the exchange rate = 3, and the 8 hour working day level is known as the LEP,d or LEX,8h.

In America, the *exchange rate* defined in the OSHA standard is 5 dB and their 8 hour workplace average level is known as time weighted average. For other US *exchange rates* and threshold levels the average level for the measurement duration is known as Lavg.

See also time weightings

See also other types of averaging

**Exposure** :
daily-noise-exposure •
noise dose •
sound exposure,

**Exposure** :
vibration •
vibration dose

The **Lower EAV** is 80 dBA and a
peak sound pressure of 135 dBC ≈ LCpeak

The **Upper EAV** is 85 dBA and a peak sound pressure of 137 dBC ≈ LCpeak

For hand arm vibration the *EAV* is 2.5 m/s² A(8)

For whole body vibration the EAV is 0.5 m/s² A(8)

See also noise dose • sound exposure • acceleration equivalent level • vibration dose value

**For noise the daily or weekly exposure is** 87 dBA and a
peak sound pressure of 140 dBC.

For *hand arm vibration* the ELV is 5 m/s² A(8)

For *whole body vibration* the ELV is 1.15 m/s² A(8)

See also
noise dose
sound exposure •
acceleration equivalent level •
vibration dose value

See also noise dose

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