To the Editor.—The article by Dr. Jerger which appeared in the October Archives (92:311-324, 1970) brings together some important data and observations on the clinical use of impedance audiometry with the Madsen, Model ZO 70 Electroacoustic Impedance Bridge. Generally, my clinical and research experiences1,2 with this same instrument support the observations made by Jeger with a few exceptions, especially, regarding the intra-aural muscle reflex (acoustic reflex) and the technique used in tympanometry. These are as follows:
First, in a study which used a pediatric population,1 it was found that when hearing was defined as normal only if there were no history of recent or chronic upper respiratory infection, hearing for pure tones and speech was no poorer than 15 dB (re: ISO 1964), and ears were found to be otoscopically normal by an otolaryngologist, the intra-aural muscle reflex was consistently present in this population. However, as Jerger