TABLE 2.

Averaged low-, mid-, high- and ultra-high frequency groups.

Group	Category	Frequencies averaged (Hz)
Group 1	Low-frequency average	125, 250 and 500
Group 2	Mid-frequency average	1000 and 2000
Group 3	High frequency average	4000 and 8000
Group 4	Ultra-high frequency average	10 000 and 12 500