Spectrogram of recording of tone from tuning fork. Horizontal axis is time axis, labeled in units of seconds along top. Vertical axis is frequency axis, labeled in units of kHz (1 kHz = 1000 Hz) along left side. Bright band is centered on frequency 262 Hz, the frequency for tuning fork tone. Background features of spectrogram come from faint background noise, largely inaudible, present during recording process.