Search PubMed⌕ Search

Biomedical subjects

B Erlandsson

Publications and source records attributed to B Erlandsson.

32 records · Page 2Linked to original sources
PubMed1979

Comparison of the hearing threshold measured by pure-tone audiometry and by Békésy sweep audiometry.

The hearing thresholds of 115 subjects, workers in a shipyard, were determined both by Békésy sweep audiometry and by conventional individual pure-tone audiometry at fixed audiometric frequencies. The Békésy method gave the lowest values for the hearing thresholds. It has been possible to find a useful linear relation between pure-tone and Békésy hearing thresholds. With the help of a retest experiment it has been established that the standard deviations of hearing thresholds, obtained under similar conditions in a pure-tone investigation, are about twice as large as those obtained in a Békésy investigation.

Adult↗
PubMed1979

Comparison between stationary and personal noise dose measuring systems.

In most of the investigations which have been made to survey occupational noise, a stationary sound level meter has been used either alone, or in combination with a stationary dosimeter. In this investigation, which was performed in a ship-building yard, an ear-borne noise dosimeter has been used. The Leq values which were obtained have been compared with those of the pocket-borne dosimeters. In many processes, considerable differences exist between pocket-borne and ear-borne dosimeters.

Acoustics↗
PubMed1979

Comparison of the hearing threshold measured by manual pure-tone and by self-recording (Békésy) audiometry.

The hearing threshold of 115 subjects aged 25--63 years and working on a shipyard were determined both by Békésy sweep audiometry and by conventional manual octave pure-tone audiometry at fixed audiometric frequencies. The attenuation rate was 2.5 dB s-1 with pulsed-tone presentation and the sweep time from 0.25 to 10 kHz was 400 s for the Békésy audiometer. Manual pure-tone audiometry was performed in 5-dB steps. The Békésy method gave the lowest values for the hearing thresholds. It has been possible to find a useful linear relation between pure-tone and Békésy hearing thresholds. With the help of a retest experiment, it has been established, that the standard deviations of hearing thresholds obtained under similar conditions in a pure-tone investigation are about twice as large as those obtained in a Békésy investigation.

Adult↗
PubMedDate not supplied

The effect of static middle ear pressures on the hearing threshold.

The effect of static tympanic pressure gradients on hearing sensitivity was studied by introducing relative underpressure of 5, 10 and 15 cmH2O in the middle ear cavity of six normal ears. A self-recording Békésy audiometer was used to measure the hearing threshold shifts during middle ear pressure equilibrations. The threshold loss was most prominent for 0.5 and 1 kHZ and less for 4 kHZ. A threshold gain was shown for 2 and 6 kHZ. Over all test frequencies the threshold shifts were increased with higher relative underpressure in the middle ear cavity. In order to evaluate the hearing impairment caused by noise, it is therefore important to control the middle ear pressure before hearing is tested. A small change in middle ear pressure can be ignored when using the summed hearing thresholds between 2 and 8 kHZ.

Audiometry, Pure-Tone↗
PubMedDate not supplied

Patency tests of the maxillary ostium--model experiments.

The function of the maxillary ostia (phi 0.22-4.7 mm) has been evaluated in experiments on a nose-sinus model with variable sinusal volumes. A piston-pump producing to-and-fro volumes of 467 cm3 of air per revolution was used at a speed of 10 and 20 revolutions per minute (rpm). Three different techniques were used: simultaneous pressure recording in the sinus and the nose (Method I); simultaneous recording of the differential pressure between nose and sinus and the air-flow through the ostium (Method II); recording of the pressure rise inside the sinus upon the application of a constant artificial air-flow of 16,7 cm3 . s-1 or 2.0 cm3 . s-1 (Method III). All variables were recorded on an ink-jet recorder and onto tape when using methods I and II for later analysis on an x-y recorder. A pressure relationship of 1 : 1 was found between nose and sinus, independently of ostial diameters, sinusal volumes and piston-pump rates. The first method did not permit an isolated determination of the ostial function as the pressure values recorded are affected by ostial diameters, sinusal volumes and piston-pump rates. The pressure-flow relationship recorded with the second method was found to be dependent only on the ostial diameters. Hysteresis was observed at ostial diameters less than or equal to 1.63 mm. This is due to ostial diameter, sinusal volume and the rate of the nasal pressure changes. This method is suitable for an isolated determination of the ostial resistance, from which the equivalent ostial diameter can be calculated. With the third method using static air-flows and pressures the results are independent of the sinusal volume. This method is suitable for estimation of the ostial airway resistance and the equivalent ostial diameter. A striking similarity was observed between the results obtained with the last two methods in estimating equivalent ostial diameters.

Airway Resistance↗
PubMedDate not supplied

Transmission of square wave pressure pulses through the perilymphatic fluid in cats.

The inner ear hydrodynamics have been studied in a series of experiments on cats. A detailed analysis has been made of the perilymphatic pressure response to square wave pressure pulses applied to the ear canal and middle ear. It was found that the initial pressure response was followed by a rebound pressure response of the opposite phase. It was also found that in most cases each phase of the pressure response could be expressed in terms of two time constants. When the cochlear aqueduct was patent, the perilymphatic pressure response showed almost equal positive and negative pressure changes. However, when the cochlear aqueduct was surgically blocked, the perilymphatic pressure response consisted almost exclusively of the first phase of the response, while the rebound phase disappeared almost completely. The possibility of influencing the inner ear fluid balance in Meniere's disease by external pressure changes is discussed in the light of the present experimental results.

Animals↗
PubMedDate not supplied

Transmission of complex pressure waves through the perilymphatic fluid in cats.

The response of the perilymphatic fluid to complex pressure waves, composed of low-frequency sine waves superimposed on square-wave pressure pulses of varying amplitude was studied. In cats with a patent cochlear aqueduct a pronounced positive pressure change could be induced in the perilymphatic fluid when complex pressure waves were used. The time constants associated with the stabilization of the perilymphatic pressure after the application of pressure complexes were longer than those associated with square-wave pulses alone. The results indicate that the functional patency of the cochlear aqueduct could be influenced by the transmission of complex pressure waves. The results also indicate that when trying to influence the inner ear hydrodynamic balance in patients with Meniere's disease, the effect of complex pressure waves is far superior to the effect of square-wave pressure pulses in patients with an open cochlear aqueduct.

Animals↗
PubMedDate not supplied

Comparison between hearing threshold measurements made with and without the aid of an ear speculum.

The hearing threshold levels of a small group of shipyard workers having differing degrees of hearing impairment were measured five times using the following audiometric techniques: fixed-tone Békésy audiometry with MX 41/AR cushions, fixed-tone Békésy audiometry with an ear speculum, and sweep-frequency Békésy audiometry with an ear speculum. From these data the mean standard deviations of the hearing threshold levels for the frequencies 0.5, 1, 2, 3, 4, 5, 6, 7 and 8 kHz were calculated, thus giving a measure of the accuracy of each method. The hearing threshold levels obtained by the three methods are compared, and the merits of data handling, expressing hearing threshold levels in pascals rather than decibels, are also discussed.

Audiometry↗
PubMedDate not supplied

Hair cell damage in the inner ear of the guinea pig due to noise in a workshop.

Guinea pigs were exposed to noise in various workshops at a shipyard. The equivalent sound level ranged from 87 to 90 dB(A) and the exposure time was 30 days of 8 hours. The numbers of lost outer hair cells were greater than in control animals, thus establishing a relation between the number of lost hair cells and the total noise dose. A comparison between the results obtained here and results obtained in laboratory experiments shows that although many physical sound parameters may be identical, the effect on the hair cells can be quite different. In particular, the total noise dose is not a parameter which can be directly related to hair cell loss. The most probable explanation for the difference in damage between the laboratory and workshop animals seems to be the rest periods of 16 hours between each of the 8-hour exposure periods.

Animals↗