Part 4 : Spectrogram comparaisons
Spectrogram is another representation of frequency versus time of a track. For each channel (right and left), horizontal axis represents time, and the vertical axis represents frequency. The amplitude is represented by the intensity (brightness) of the color of each point in the image.
For the spectrogram of the Ed1 vinyl, the blue arrow shows the limit corresponding to the sampling frequency of the master. We can also see that not all tracks have the same high frequency limit. The yellow arrow shows the harmonics created by the vinyl playback method.
The Ed2 CD shows the frequency limit at 22kHz (purple arrow) with tracks rising to a lower limit (yellow arrow). The black area (white arrow) shows that there is no signal above 22 kHz, which is normal for a 44.1 kHz sampling rate.
The Ed7 Streaming shows the frequency limit at 20kHz (black arrow) . The black area (white arrow) shows that there is no signal above 24 kHz, which is normal for a 44.1 kHz sampling rate.
The Ed3 bluray concert video PCM and Ed6 binaural versions are similar in their spectrogram. We find the frequency limit at 24 kHz (purple arrow) and a track that has a lower frequency limit (yellow arrow). The black area (white arrow) shows that there is no signal above 24 kHz due to the 48 kHz sampling frequency..
We find the same analyse between the 5.0 version (Ed4 and Ed5) and the digital stereo versions. The purple arrow shows the frequency limit at 24 kHz confirmed by the black area above (white arrow). The yellow arrow also shows a song that has a lower cutoff frequency as for the Ed3 and Ed6 versions..