For example, one might refer to the A above middle C as a', <answer>A4</answer>, or 440 Hz. In standard Western equal temperament, the notion of pitch is insensitive to "spelling": the description "G4 double sharp" refers to the same pitch as <answer>A4</answer>; in other temperaments, these may be distinct pitches. Human perception of musical intervals is approximately logarithmic with respect to fundamental frequency: the perceived interval between the pitches "A220" and "<answer>A4</answer>40" is the same as the perceived interval between the pitches <answer>A4</answer>40 and A880. Motivated by this logarithmic perception, music theorists sometimes represent pitches using a numerical scale based on the logarithm of fundamental frequency. For example, one can adopt the widely used MIDI standard to map fundamental frequency, f, to a real number, p, as follows
The description "G4 double sharp" refers to the same pitch as what?
A4