| Deutsche Version |
| 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. |
| Formula for the RMS noise voltage: |
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| 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 + |
| 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. |
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.
| 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: Noise figure NF = 10 log (noise factor F) in dB Noise temperature Te = T0 (F − 1) It is determined by EIN means Equivalent Input Noise. It is a specification that helps measure the Signal-to-noise ratio, often abbreviated SNR or S/N, is an electrical engineering |
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