The units of level in the detection and discrimination test are not equal. Confusion may arise because they are both called dB HL*. However the asterisk refers to a different reference level in both tests. This is due to the fact that the discrimination test is a supraliminal test by design, while the detection test is not.
In the Phoneme Discrimination:
- A 1 kHz narrow band noise of 70 dB HL was presented in a loudness balancing task in normal hearing subjects to balance the phonemes at the 70 dB supraliminal level.
- 70 dB HL* in this test means that the phoneme is perceived equally loud as a 70 dB HL 1 kHz NBN by the hearing population.
In the Phoneme Detection:
- All phonemes were loudness balanced at threshold level.
- 70dB HL* in this test means that the phoneme is presented 70 dB above the detection threshold level.
For more details on the balancing procedure, please find attached a publication on the construction of both tests (Govaerts et al., 2006).
Pages 93-94 describe the loudness balancing for the discrimination task. Page 102 explains the balancing of the detection test.