Gordon Flottorp

The acoustic stapedius reflex in relation to critical bandwidth.

The threshold of the acoustic stapedius reflex in man was investigated by means of changes in acoustic impedance of the ear. The contralateral ear was stimulated by using bands of noise and complex tones with various bandwidths. The experiments showed that the reflex threshold, expressed in decibels re 2.10−6 N/m2, is almost constant for bandwidths less than a specific value and designated as “critical bandwidth.” When the bandwidth was further increased, a decrease in the reflex threshold at approximately 3–6 dB/oct was observed. Assuming that the stapedius reflex mechanism is loudness governed in persons with normal hearing, these findings confirm the existence of a critical bandwidth in loudness summation. In addition, the findings indicate that the basis for the critical‐band mechanism is located in the peripheral part of the auditory system, probably in the cochlea.

Size And Duration of Acoustically Elicited Impedance Changes in Man

The results of the present investigations show:1) The threshold for the acoustically elicited impedance changes is lower for white noise and low frequency stimuli than for high frequency stimuli.2) The size of the acoustically elicited impedance changes is larger for low frequency stimuli than for high frequency stimuli of the same intensity above the impedance threshold.3) The increase of impedance change as a function of increased stimulus intensity is faster for low frequency stimuli than for high frequency stimuli.4) The duration of the acoustically elicited impedance changes is longer for continuous low frequency stimulation of the same intensity above the impedance threshold.5) As far as the impedance change of the middle ear is considered a protective mechanism for noise induced hearing loss, our results indicate that the inner ear in this respect is better protected when exposed to low frequency sound than to high frequency sound.

Phytanic acid storage disease Hearing maintained after 15 years of dietary treatment

Heredopathia atactica polyneuritiformis is a biochemically defined disease with a specific dietary treatment. It is an autosomal inborn error of metabolism. The phytanic acid is of exogenous origin and stems mainly from preformed phytanic acid in foods. In two Norwegian patients, serum phytanic acid has been brought down to normal levels and one of them has been followed for 15 years. During this period of dietary treatment there was no worsening of hearing.

Mechanical impedance of human headbones (forehead and mastoid portion of the temporal bone) measured under ISO/IEC conditions

Mechanical impedances of the mastoid portion of the temporal bone and of the forehead are presented for 60 human subjects of both sexes and of ages between 9 and 71 years. Measurements were carried out using a plane circular surface of 1.75 cm2 and a static force of 5.4 N (ISO/IEC conditions). Impedance is found to vary with age and to a lesser extent with sex. Results are consistent with earlier measurements carried out under somewhat different conditions, but deviate rather substantially at most frequencies from the recommended ISO/IEC mechanical impedance for an artificial headbone. A study of the influence of variations in the mechanical headbone impedance upon bone vibrator performance by means of an analogous electrical network is reported.Subject Classification: [43]65.64; [43]85.20.

Improving Audiometric Thresholds by Changing the Headphone Position at the Ear

A 10-year noise project, consisting of annual hearing measurement, temporary threshold shift (TTS) measurements and examination of noise exposure in 250-300 employees, involved a study of the improvement in measured hearing threshold by changing the position of the headphone at the ear. Threshold measurements were performed at 11 frequencies ranging from 125 to 8,000 Hz, and consisted of 2,708 audiograms in the hearing control program and 551 audiograms in the TTS program. A new threshold determination at frequencies above 3,000 Hz was carried out after moving the earphone to a new position in 870 (32%) of the cases in the hearing measurement program and 248 (45%) of those in the TTS program. The indication for moving the phone is discussed. Improved thresholds in the range of 5-40 dB at 6,000 and 8,000 Hz were observed in 58-68% of the cases, depending upon frequency and program (measurement of hearing and TTS). Consequences for standard threshold values and for diagnostic purposes are discussed.

The effect of ear protectors against sound waves from explosions.

In civilian life and the military services people have their hearing damaged by sound from explosions. Measurement of this sound and the effect of ear protectors against it has met with technical difficulties. The authors show an experimental set-up for the measurement, and give data on the effect of some ear protectors.

Morbus Menière — Cerebral Atrophy: A Preliminary Report

At Rikshospitalet in Oslo, 20 randomly selected patients with a classical picture of Menieres disease have been investigated. The results indicate that the tissue damage and functional disturbances giving rise to Menieres disease are not limited to the labyrinth alone, but that the central nervous system is also the seat of pathologic changes. Further investigations are being carried out.