Muriel M. Woodhead

Effect of Brief Loud Noise on Decision Making

An experiment was designed to investigate whether irrelevant loud bursts of low‐frequency noise affected decision‐making unfavorably. Analysis of the results revealed a significant decrement in performance due to the noise distraction. Scores for the whole of a 4‐min test were unimpaired because only those responses immediately following the noise were affected. A second experiment demonstrated that effects were related to intensity.

Searching a visual display in intermittent noise

Abstract An experiment was carried out to investigate the possible effects of auditory distractions when the visual task was to search a display in which random numbers were presented at a rate of five per second. A circle round any number was an instruction to the observer to cross off repetitions of that number, changing to a new one whenever another circle appeared. There were three auditory conditions: (a) brief bursts of noise at 110 dB SPL, (b) bursts at 70 dB, (c) always quiet. (b) and (c) were alternative experimental controls. It was found that the number of errors in the whole of a 15-min search did not differ between the three conditions, but searching was less efficient in the half-minutes following the bursts at 110 dB compared with the same periods in either control. The errors which occurred more often in loud noise were of a particular type: failure to notice the circles. It is suggested that noise increased the observers general level of activity, enlarging differences which the need to monitor two unequally occurring features of the display, circles and numbers, had already established.

Performing a visual task in the vicinity of reproduced sonic bangs

Abstract Recorded sonic bangs accompanied a fast visual task performed by subjects working indoors. The sound pressure levels of the bangs corresponded to the indoor stimulation experienced for outdoor sonic bangs of 0·80 lb/ft 2 to 2·53 lb/ft 2 . Performance on the visual task was temporarily impaired when the sonic bangs were at the highest level. This was above the level of loudness set as an upper limit around airports for existing aircraft.

Comparisons of Training Techniques for Complex Sound Identification

Fourteen different synthetic engine sounds were mixed with five different synthetic cavitation sounds at realistically difficult signal‐to noise ratios. Eighty one Royal Navy ratings, divided into eight training groups, were asked to identify the 14 engine sounds. Training procedures were varied among groups to answer some questions pertinent for programming a teaching machine. It was found that (1) verbal descriptions of the actual physical characteristics of the sounds give better results than those supplied by experienced listeners, (2) the order in which training items are presented is important. The most useful order involved changing one relevant quality per item, (3) “good” high engine‐to‐cavitation ratio) recordings may be an advantage if alternated with realistically “bad” ones, (4) feedback (knowledge‐of‐results) procedures should be concentrated more at the end of a training program and recordings should be extended temporally to overlap with the feedback, (5) a large population of engine noise...

Perceptual Confusions between Four‐Dimensional Sounds

Are meaningless sounds learned and identified in a speech mode? Sixteen sounds were generated differing on four dimension, each having two values. These were: the source waveform contained either all harmonics or odd harmonics; the fundamental frequency was either 90 or 142 Hz; there were either one or two formant frequency regions; and the formant(s) was (were) either low, 600 (and 1550) Hz or high, 940 (and 2440) Hz. Twenty‐four listeners identified these sounds. Fewer confusions were made between sounds (1) as the number of dimensions on which they differed increased, and (2) as the dimension(s) changed, from formant number to ferment frequency region, to fundamental frequency, to source waveform. Similarly, fewer confusions were made between sounds whose formant frequencies and fundamental frequency were in a fixed ratio than between those with the same formant frequency. In essence fixed ferment sounds were more often called the same sound than were fixed ratio sounds. The data fit a hypothesis that ...

On the recovery of physical dimensions of stimuli, using multidimensional scaling

The results of three confusion experiments (acoustic presentation, visual presentation, and combined acoustic and visual presentation of the stimuli), involving artificial sounds constructed from four physical parameters, are analyzed using nonmetric multidimensional scaling (MDS). It appears that just three of the physical parameters are important in the confusions of these sounds in all three cases. The parameter sets used in the combined and visual presentation experiments were identical and differed from that used in the acoustic presentation experiment.Subject Classification: [43]65.75, [43]65.58.

Identifying Meaningless Tonal Complexes

Series of buzz tones with up to 24 harmonics were presented to five groups of listeners for identification. Nine tones in which different harmonics were emphasized were presented to Group I who could easily tell them apart and could identify them with 33% accuracy. The remaining groups heard three of the tones in various conditions of noise, filtering, fundamental frequency, and emphasized to nonemphasized harmonic intensity differentials. The most difficult task was to identify the tones with differing harmonic structure when the fundamental frequency was not the same for every complex tone. It was also difficult to pick out complexes with the same harmonic structure and basic frequency when noise‐masked, filtered, and in‐quiet items were intermixed at random in the same test. The distinguishing differences in the meaningless buzz complexes were in harmonics six and above.

Value of Ear Defenders for Mental Work during Intermittent Noise

Ear defenders were worn for protection against the distracting effects of bursts of loud, but not unacceptable, noise during a mental task. Two types of noise were used: one characterized by high and the other by low frequencies. Performance was better with defenders than without them. The improvement was particularly marked with the high‐frequency burst.

Acoustic stereotypes in the interpretation of unfamiliar telephone signals.

International dialling has brought with it the problem of recognizing whether an unfamiliar telephone sound means a ringing or an engaged signal. On the evidence of 60 British listeners, our national stereotype appeals to be based on the repetition period and degree of complexity of British tone signals. Short, unmodulated sounds in foreign systems are judged to be engaged, longer complex ones to be ringing.

Identifying diesel engine sounds

Abstract Naval ratings were given the task of identifying the sounds of three lorry diesel engines at running speeds of 1000, 2000 and 3000 rev/min. The physical signal was varied by adding thermal noise and by multiplying all frequencies by factors of 1, 2, 4 and 8. The experimental variables were knowledge of results, amount of cueing, and the meaningfulness of the identifying names. Meaningfulness consisted either of code names or of the real names plus a description of the physical characteristics of the engine. Where real names were in use, identification was more accurate even with frequency multiplication. Engine types were identified better than engine rev/min. The accuracy of engine identification decreased as the noise masking increased and as the frequency multiplications changed from × 1 to ×2 to ×8 to ×4. However, when noise masking was absent, engine identification at the ×8 speedup yielded scores equal to ×1 and ×2. The rev/min identifications were all equivalent except at ×4 in noise, which always gave the lowest score.