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Biomedical subjects

B Almqvist

Publications and source records attributed to B Almqvist.

9 recordsLinked to original sources
PubMed1995

Performance of electronic Morse decoders in decoding telegraphy masked by noise.

The performance of five different electronic Morse decoders in decoding telegraphy signs (Morse code) consisting of 800 Hz pure tones masked by a narrow-band noise with a bandwidth of 185 Hz (1/3 octave 713-890 Hz) centred at 800 Hz and a broadband noise (100-2,500 Hz) was studied at 20, 40, 80, 150 and 200 signs/min telegraphy speed. In steps of 1 dB the S/N ratios were varied from high values where 100% was recognized to low values where nothing was recognized. At narrow-band masking noise with 80 and 150 signs/min telegraphy speed a S/N ratio varying from +8 to +12 dB and +8 to +11 dB respectively was required for 100% recognition. At broad-band masking noise the S/N ratios required for 100% recognition varied from -4 to +3 dB at 80 signs/min telegraphy speed and -3 to +3 dB at 150 signs/min telegraphy speed. When compared to earlier findings in our laboratory concerning human recognition of Morse signs it seems that man outperforms electronic Morse decoders at low S/N ratios and low to moderate telegraphy speeds (< 100 signs/min).

Auditory Perception↗
PubMed1992

Recognition of telegraphy signs at different listening levels and frequencies.

The recognition of telegraphy masked by noise at 40 and 80 signs/min telegraphy speed was studied in 10 normal-hearing subjects at different sound pressure levels (25-85 dB SPL in steps of 5 dB) as well as at different test frequencies (2000, 1000, 800, 630, 500 and 250 Hz). The ability to recognize the signs varied with varying SPL. Recognition for most of the subjects was best at an SPL close to 70 dB. All subjects improved their recognition as the frequency was lowered to 500 Hz, some even at 250 Hz. These facts should be taken into consideration when training telegraphy operators as well as in the construction of radio receivers to permit listening at low frequencies. Furthermore, the critical ratio was calculated at the different test frequencies.

Acoustics↗
PubMed1991

Recognition of telegraphy disturbed by noise at different S/N-ratios and different telegraphy speeds. A comparison to short-tone audiometry.

The ability to recognize telegraphy at different S/N ratios and telegraphy speeds was compared for 10 normal-hearing men trained in detecting telegraphy. The ability to recognize telegraphy disturbed by noise decreased with increasing telegraphy speed and reduced S/N ratio. The recognition of telegraphy disturbed by noise seems to follow the relations known from experiments with short-tone audiometry.

Adult↗
PubMed1989

Phase audiometry--a rapid method for detecting cerebello-pontine angle tumours?

Four groups of subjects have been investigated, using a manual phase audiometer. Group 1 consisted of 20 normal-hearing subjects. Group 2 of 22 subjects with unilateral or asymmetric cochlear hearing loss. Group 3 of 14 subjects with surgically verified CPA tumours, and Group 4 of 15 subjects with unilateral conductive impairment. In this report we suggest an upper borderline value for detecting interaural time differences of 120 microseconds. If the subject is able to detect only a value exceeding 120 microseconds, there is likely to be a retrocochlear lesion.

Adolescent↗
PubMed1987

Effects of low-frequency components and analog filtering on auditory brainstem responses. A comparison of analog and digital filtering.

Analog and digital filtering of ABR (Auditory Brainstem Response) is compared for 20 adults with normal hearing. The result shows that the shape of the ABR is changed by the non-linear phase function of the analog filter (350-1,700 Hz). Peaks IV and V are particularly affected. The result also shows that if peaks IV and V are to be identified with certainty it is sometimes necessary to raise the lower band limit of the filter. This is because the low-frequency part of the ABR interferes with peaks IV and V. The latencies of peaks I to V obtained from ABRs after digital and analog filtering have been compared. This showed small but significant differences.

Adult↗
PubMedDate not supplied

Objective intraoperative method to record averaged electromyographic stapedius muscle reflexes in cochlear implant patients.

We have developed a procedure to measure the averaged stapedius muscle reflex in response to electrical stimulation (AESR) with a cochlear implant. The AESR, as activated by ipsilateral stimulation with a cochlear implant, was investigated intra-operatively in a series of 12 children. After the cochlear implant was placed into the cochlea and secured by the surgeon, an electromyographic (EMG) needle electrode was gently placed into the stapedius muscle. During stimulation of the cochlear implant, the stapedius reflex was monitored visually (VESR) and as an averaged EMG response (AESR). Consistent AESRs were obtained in 7 of the 12 children. These measures provide a method to obtain stapedius muscle responses that may be helpful in the programming of young children with cochlear implants. Comparative post-operative measures were also obtained, including behavioral threshold levels, behavioral comfort levels, and the contralateral stapedius reflex threshold (ESR) on selected electrodes.

Auditory Threshold↗