The humming is primarily caused by magnetic forces, which are proportional to current.  Less loaded transformers have less current thru them, so hum less.

Why do some transformers hum less or not at all when lightly loaded?
For example, a bit or a boolean can be either 0 or 1 so the number 2 is associated with it. Similarly, for a byte which is 8 bits, the maximum number of different assignments would be 2^8.

Is there a name for this number?

When we pass everything through our system that has ECMAScript, Java and MySQL, then a boolean does not have only two possible assignments. For instance, a false boolean gets saved as a 0 and the boxed value could be null so a boolean suddenly can get true, false, 0, 1, null or even undefined or &lt;missing&gt;.

I think it could get problematic in tests to guarantee that the values are not inconsistent. For instance, a value boolean locked could become null and then when a script or a layout template evaluates it then it will evaluate to false somewhere if the real value was null and similar problems.

So why don't we always assert that a boolean has the same number of possible values (2 values) and similarly for other types?

There is a mathematical term named "arity" that is something similar but not exactly, and statistics and probability theory also has the concept of "event space" that would be almost exactly what I mean. For instance, the event space for a boolean would be the set {0,1} which has cardinality 2 and that cardinality doesn't get preserved throughout the system, especially when data is passed as polyglots and/or serialized (json, jsonp, xml, yaml).
