This is machine translation

Translated by Microsoft
Mouseover text to see original. Click the button below to return to the English version of the page.

Note: This page has been translated by MathWorks. Please click here
To view all translated materials including this page, select Japan from the country navigator on the bottom of this page.


Convert magnitude to decibels


ydb = mag2db(y)



ydb = mag2db(y) expresses in decibels (dB) the magnitude measurements specified in y. The relationship between magnitude and decibels is ydb = 20 log10(y).


collapse all

Design a 3rd-order highpass Butterworth filter having a normalized 3-dB frequency of rad/sample. Compute its frequency response. Express the magnitude response in decibels and plot it.

[b,a] = butter(3,0.5,'high');
[h,w] = freqz(b,a);

dB = mag2db(abs(h));

xlabel('\omega / \pi')
ylabel('Magnitude (dB)')
ylim([-82 5])

Repeat the computation using fvtool.


Input Arguments

collapse all

Input array, specified as a scalar, vector, matrix, or N-D array. When y is nonscalar, mag2db is an element-wise operation.

Data Types: single | double

Output Arguments

collapse all

Magnitude measurements in decibels, returned as a scalar, vector, matrix, or N-D array of the same size as y.

See Also

| | |

Introduced in R2008a

Was this topic helpful?