Specific loudness N′ as a function of critical band rate z: The left plot shows the measurement recordings A to F along with the reference stimulus, while the right plot depicts the stimuli used in the listening experiments after being auralised and equalised to 60 dB(A). The top panel on the right displays the stimuli from the first heat pump (A–F), whereas the bottom panel shows the stimuli from the second heat pump (a–f), each compared with the auralised reference, also at 60 dB(A). Depicted are the values for the left ear.