Songbirding Under 5kHz
For those with high-frequency hearing loss there is a modified version: Songbirding Under 5kHz. This version alters all sound above 5kHz down to half (one octave down, in musical terms).
To listen to this version visit the Under 5kHz site at 5kHz.songbirding.com.
On YouTube you can find video versions that include audio spectrograms.