White noise vs Black body radiation

[xfshi2000]

Hi all:
I am confused about one question. When we detect signal from human brain using coil in Nuclear Magnetic Resonance, two source contribute noise to our signal. One is coil itself. The other is human brain. Why can we think the noise from human brain is white noise? Can we compare the noise generated by human brain with that emitted from black body radiation? I know for a resistor, we consider it as approximation black body for current. I hope to know what cause white noise of human brain? thanks for your help.

xf

 

[Bob S]

The thermal noise across a resistor is called the Johnson or Nyquist noise. See
http://en.wikipedia.org/wiki/Johnson–Nyquist_noise
It is about v = sqrt(4kTBR)
where k= Boltzmannn constant
T = temperatore in degrees K
B= bandwidth in Hz
R = ohms

Bob S

 

[astrokreng]

Hello xf,

Thank you for your question. Let me first clarify the difference between white noise and black body radiation. White noise refers to a type of random signal that has a flat power spectral density, meaning that all frequencies within a certain range are present with equal power. This type of noise is often used as a reference for other types of signals. On the other hand, black body radiation refers to the electromagnetic radiation emitted by a perfect absorber and emitter of all wavelengths, known as a black body. This type of radiation has a characteristic spectral distribution that depends only on the temperature of the body.

In the case of detecting signals from the human brain using a coil in Nuclear Magnetic Resonance, both the coil and the human brain contribute to the noise in the signal. The noise from the coil is typically considered white noise because it is due to random fluctuations in the electronic components of the coil. However, the noise from the human brain is more complex and cannot be easily classified as white noise. This is because the human brain is not a perfect absorber and emitter of all wavelengths, like a black body. Instead, the noise from the brain is a combination of various sources, including thermal noise from the neurons, electrical noise from the brain cells, and environmental noise from outside sources. Therefore, it cannot be directly compared to black body radiation.

In conclusion, while the noise from the coil can be considered as white noise, the noise from the human brain is more complex and cannot be classified as white noise or compared to black body radiation. I hope this helps to clarify your confusion. Let me know if you have any further questions.