Experimental design for the sequentially exposure to noise (Leq8h= 98.8 dB SPL) and gentamicin (40 mg/kg for 8 days) OBN8kHz: octave band noise centred at 8 kHz. G+N group: group exposed to noise and treated with gentamicin. GN1,2,3: group treated with gentamicin and exposed to noise, one, two or three weeks after the end of the treatment. D= day, w=week