A 5000-Hz tone must have what sound level to seem as loud as a 50-Hz tone that has a 78-dB sound level?

Answer 1

Not sure if you need calculations or not but if you use the equal loudness contour for 80 dB (closest to 78) a 5000 Hz tone would have 87 dB SPL and a 50 Hz tone would have 102 dB SPL. Therefore the 50 Hz tone would need to be 15 dB Higher which would be 93dB