Calculation of thermal noise signal-to-noise S/N temperature bandwidth volts dB decibels noise figure - sengpielaudio Checker
 
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• Calculation of Noise voltage: Thermal noise •

Johnson noise, Nyquist noise, and white noise
Noise voltage in microvolts (RMS), noise level in dBu, and dBV
Hi-Fi bandwidth from 20 Hz to 20 000 Hz = 19 980 Hz
In common use, the word noise means unwanted sound or noise pollution.
In electronics noise refers to the electronic signal corresponding to
acoustic noise in an audio system.

Temperature theta   °Celsius
Used bandwidth Δ f    Hz
Resistance R   ohms
     
↓           
     
RMS Noise voltage Vn  μV (microvolts)
Noise level Lu  dBu 
Noise level LV  dBV 
Formula for the RMS noise voltage:

Rauschspannungs-Formel - sengpielaudio		 White noise

The noise level Lu in dBu has the reference voltage V0 = 0.7746 V ≡ 0 dB
and the noise level LV indBV has the reference voltage V0 = 1 V ≡ 0 dB.

Boltzmann constant  kB = 1.3806504×10-23 J/K (joule/kelvin); J = W · s
Absolute temperature in kelvin  T = 273.15 + theta in °C
Bandwidth being considered  Δ f = f2 − f1 = fmax − fmin in Hz; 20 kHz − 20 Hz = 19980 Hz
Resistance of the circuit element 
 		 R.
R does not mean the universal gas constant!

To each noise potential the temperature T and the bandwidth Δ f
must be indicated, with which it was measured.

Enter a value in the left or right box, then press the TAB bar or make
a mouse click at an empty space at the side, to get the solution.
The calculator works in both directions of the ↔ sign.

Noise voltage level (audio) LV:
dBu		  ↔  Noise voltage (audio) V:
µV (microvolt)
Noise voltage level   Noise voltage
Reference voltage V0 = 0.7746 Volt = 774 596.67 µV ≡ 0 dBu
Noise voltage level LV:
dBV		  ↔  Noise voltage V:
µV (microvolt)
Noise voltage level   Noise voltage
Reference voltage V0 = 1.0 Volt = 1 000 000 µV ≡ 0 dBu

Don't forget the minus sign, when you enter the noise voltage level.

Sound engineers or technicians with good ears
will never ask for noise power or energy.
What moves our ear drums?
What moves the diaphragm or membrane of the
microphone of a sound pressure level meter
(SPL meter)? Try to avoid the sound power
(acoustic power).

 
Note: The radiated sound power (sound intensity) is the cause -
and the sound pressure is the effect.
The effect is of particular interest to the sound engineer.
The effect of temperature and sound pressure.
 

 
Acousticians and sound protectors (noise fighters) need the
sound intensity (acoustic intensity). As a sound designer you
don't need that; look out more for the sound pressure as an
effect to your ears and to the microphones.
 

Sound pressure and sound power

Noise fighters (noise protectors) think differently. This is a special sound engineering site.
When you think of avoiding reflections by impedance matching (power matching) with Zin = Zout
that has only to do with high frequency RF, and not with audio.

White Noise Generator

Thermal noise: Also called Johnson noise, is the random white noise generated by
thermal agitation of electrons in a conductor or electronic device. It is produced by
the thermal agitation of the charges in an electric conductor and is proportional to
the absolute temperature of the conductor. It manifests itself in the input circuits of
audio equipment such as microphone pre amps, where the signal levels are low.
The thermal noise level is the limiting minimum noise any circuit can attain at a
given temperature. Modern high-quality microphone pre amps, under proper
conditions, have noise specifications that come very close to this theoretical limit.

Noise figure NF or noise factor F:
The Noise factor of a transducer at a specified input frequency is the ratio of (a/b)
where "a and b" are:
a) the available Signal to Noise Ratio (SNR) at the signal generator terminals per
unit bandwidth when the temperature of the input termination (generator or source)
is (usually 20°C = 293.15 K) and the bandwidth is limited by the transducer, to
b) the available SNR per unit bandwidth at the output terminals of the transducer.

Noise figure NF = 10 log (noise factor F) in dB

Noise temperature Te = T0 (F − 1)
T0 is standard temperature, usually 20°C = 293.15 K

It is determined by
a) measuring (determining) the ratio, usually expressed in dB, of the thermal noise
voltage at the output, to that at the input, and
b) subtracting from that result, the gain of the system in decibels. Typical noise
figures range from 0.5 dB for very low noise devices, to 4 to 8 dB.

EIN means Equivalent Input Noise. It is a specification that helps measure the
"quietness" of a gain stage by deriving the equivalent input noise voltage
necessary to obtain a given preamp output noise. Numerically, it’s the output noise
at a given gain setting minus the gain. EIN is usually measured at maximum gain
and typically ranges from −125 to −130 dBu.

Signal-to-noise ratio, often abbreviated SNR or S/N, is an electrical engineering
concept defined as the ratio of a signal power to the noise power corrupting the
signal. In less technical terms, signal-to-noise ratio compares the level of a desired
signal (such as music) to the level of background noise. The higher the ratio, the
less obtrusive the background noise is.

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