Adequate signal-to-noise ratio is one of the characteristics of a professionally designed sound reinforcement system.
The terms “dynamic range” and “signal-to-noise ratio” are often used interchangeably, but a closer look reveals that they are not exactly the same thing.
The dynamic range of a sound system is the difference in level between the highest signal peak that can be reproduced by the system (or device in the system) and the amplitude of the highest spectral component of the noise floor.
Every electronic device has a dynamic range that is determined primarily by the limitations of the power supply and the residual noise level of the unit.
A strong narrow band component in a device’s noise floor will limit the dynamic range of the system.
Signal-to-noise ratio is the difference in level between the average signal level and the average level of the noise floor. A device that is being driven to some average out put level with common program material should have peaks that exceed this level by 10 to 20 dB.
This is why we operate mixers near their “0” indication on their meter, and the rest of the available voltage swing is reserved for peaks in the program material.
The “average” level is of importance, because it is what we listeners (and meters) use to judge the loudness of the program.
If a voltmeter were used to measure the R. M. S. value of the device’s residual noise, the signal-to-noise ratio will be the difference in level between this value (usually expressed in dBV or dBu) and the nominal “zero” output level ex pressed using the same dB reference.
This assumes that the device is being driven to its “meter zero” which is where we like to operate most mixers to optimize their gain structure.
The dynamic range of a system (or component) is not dependent on a signal being present. It’s just the difference between the maximum possible undistorted out put level and the highest component in the noise floor (usually “A” weighted). Signal-to-noise ratio requires a signal, so it must be measured under actual use of the system or component.
A system with wide dynamic range may have poor signal-to-noise due to the way that it is operated.
Dynamic range can be used to describe the performance that is possible to achieve with a system or device, whereas signal-to-noise ratio might be used to describe what is actually achieved in practice.