signal to noise ratio (SNR)

How does matlab measure snr of an audio signal?

Why i got negative value of SNR in matlab, Because if i measure using sound level meter in real life the snr of an audio should be high?

Answer 1

[Daniel Pollard]

According to the documentation,

"r = snr(x,y) returns the signal-to-noise ratio (SNR) in decibels of a signal, x, by computing the ratio of its summed squared magnitude to that of the noise, y. y must have the same dimensions as x. Use this form when the input signal is not necessarily sinusoidal and you have an estimate of the noise."

In other words,

r can be negative because it's measured in dB, so if the sum of the squares of the noise y exceeds the sum of the squares of the signal x, the argument of the logarithm is between 0 and 1, so the logarithm is negative.

[muhammad nur adri nawi]

thank you

[muhammad nur adri nawi]

Thank you for answering my question, i have one more question sir.

If i got negative value of SNR does it mean the signal quality is low ? And how to measure noise level of a noise audio signal ? Did using fvtool function will help ?