@rdtsc @Shalvenay I found the Philips article with the textbook references. That's probably the right answer which the textbook author intended.
D. Goedhart, R. J. van de Plassche, and E. F. Stickvoort, “Digital-to-Analog Conversion in Playing a Compact Disc,” Philips Technical Review, vol. 40, no. 6, 1982, pp. 174-179
> This entire spectrum must not be passed on to the player amplifier and loudspeaker. Even though the frequencies above 20 kHz are inaudible, they would overload the player amplifier and set up intermodulation products with the baseband frequencies or possibly with the high-frequency bias current of a tape recorder. Therefore all signals at frequencies above the baseband should be attenuated by at least 50 dB. [Here baseband is the audible frequency range between 20 Hz and 20 kHz.]
