3dB bandwidth and intensity

[preethi19]

Hi i wanted to know why bandwidth was always taken in 3dB range and i read becoz thats the range of useful frequency. Ok this is fine. But for say some circuits they mention the dynamic range is 72dB or 96dB. What does this mean??? Does that mean we get useful frequency range at 72dB for that particular system. So then why standardise the 3dB range???? What exactly does dB represent for a system. Becoz for calculating bandwidth we take the lower and upper cutoff frequency at 3db and the bandwidth is (upper-lower). But say for eg 72dB information how can i determine the frequency range for which my system would work??? Is there any formula or anything. Pls help!!! THank you!!!

 

[KlausST]

Hi,

you did no research on your own.

Please, before posting, do your own research. Wikipedia, google, or even here in this forum.
At the bottom of this page there is a box with "similar threads". Please go through them.

You are always welcome to ask SPECIFIC questions.

Klaus

 

[Audioguru]

Hi i wanted to know

Your questions are about basic common knowledge but online they describe only the details.
Here is some basic common knowledge:

1) why bandwidth was always taken in 3dB range and i read becoz thats the range of useful frequency.

3dB is half or double the power (easy to measure) and is a small but noticeable change in loudness or brightness.

2) for some circuits they mention the dynamic range is 72dB or 96dB. What does this mean???

Dynamic range is how many dB from as small as you can hear or see to as loud or bright it is. Noise limits the lowest level and clipping limits the highest level.

Since 3dB is a noticeable change in level but maybe you want a bandwidth that does not have a noticeable rise or drop in its frequency response so 1dB is used instead of 3dB.

If you are in your very quiet home listening to music then maybe you want the loudest parts of music to be at 120dB and the softest at 40dB so that the dynamic range is 80dB. But if you listen in your noisy car where the noise is frequently 70dB then the dynamic range of 80dB will cause the lower 30dB of sounds not to be heard.