Sound levels during a typical major operation were measured to identify the main sources of noise in the operating theatre. Although overall sound levels were within the recommended levels for a satisfactory working environment, loud intermittent noises of up to 108 dB were emitted from sources such as suckers, "intercoms", and alarms on anaesthetic monitoring devices. The noisiest time was usually during the preparation period of the operation; during surgery, noise levels were much higher than levels of normal Preferred speech between staff. speech interference levels were often exceeded which made communication difficult and sometimes impossible. Communication and concentration were also disrupted by unnecessary background conversation.
We have measured the sound levels in the
theatre, to identify surgical procedures and items of theatre
equipment that create the most troublesome noises. Methods A complete operation (radical neck dissection) was recorded for an analysis of the overall noise levels during a typical major surgical procedure. A representative 5-min part of the recording was then analysed in more detail. Sound levels of individual items of operating theatre equipment were also studied separately to determine their frequency characteristics and the peak sound levels
they produced. TABLE
SOUND PRESSURE OPERATION
Introduction Noise ("unwanted sound") is an everyday nuisance which may have deleterious effects on the well-being and work performance of those exposed to it. Operating theatres are as susceptible to noise pollution as other working environments; Shapiro and Balandl likened the noise levels in an operating theatre to those encountered on a motorway.l Staff and patients in the operating theatre are exposed to a barrage of sounds, including those produced by ventilators, monitoring devices and alarms, suckers, diathermy machines, scavenging systems for anaesthetic gases, mechanical and pneumatic tools, heaters, pumps, paging devices, "intercoms", telephones, and by the clanging of metal bowls, instruments, and trolleys. This cacophony is often enhanced by noise from adjacent scrub-up areas, instrument rooms, and sterilisers. For theatre staff this noise can lead to impaired concentration and performance, interference with communication, and increased levels of stress, and patients who are conscious for part or all of their time in the operating theatre may become more anxious because of the noise.2-4
*Average peak sound levels occurring for more than 1 %, 10%, 50%, 90%, and 99% of respectively. The Leq is a constant equivalent sound level of the actual time-varying sound level over the penod. the time,
lin linear scale A= A scale. =
Noise during surgery was measured with two sound level meters (’B & K 2209’, Bruel and Kjaer, Copenhagen) and an inch remote microphone (B & K 4149 1/2’). These were placed centrally over the operating field and level with the surgeon’s ear, so that the recorded sound levels were similar to those heard by the surgeon. Recordings were made with a digital recording system (Sony), consisting of a ’PCM-F1’ digital audio processor, and an ’SL-F1’
ADDRESS: Royal Prince Alfred Hospital, Sydney, Australia
(B. Hodge, MB, J. F. Thompson, FRACS). Correspondence to Mr J. F Thompson, Royal Prince Alfred Hospital, Missenden Road, Camperdown, New South Wales 2050, Australia.
video cassette recorder. The frequency response of the system was 10 Hz-20 kHz (±05 dB) with 90 dB signal noise. Sounds were analysed later by means of a ’B & K 2113’ audio frequency spectrum analyser with a ’B & K 4426’ noise level analyser outputing to a ’B & K 2312’ alpha-numeric printer. A ’Nicolet 446A’ Fast Fourier computing spectrum analyser was used for frequency analysis. Sound levels of individual items were measured with the same equipment and also with a hand-held ’B & K 2203’ sound level meter.
Results The background noise level (inside an operating theatre without any activity) was 13 dB(A). Equivalent sound levels for 5 min of the representative major operation are shown in table L There was no weighting of any particular frequency across the spectrum of these levels. The main sources of sound in the theatre were as follows: Event (distance from sound) Stainless steel bowl falling onto floor (2 m) Gas escaping during change of anaesthetic gas
103 cylinder (3 m) Gas escaping from wall gas outlet during disconnection 98 of pneumatic tourniquet (3 m) 98 Anaesthetic tube holder falling onto floor (3 m) 90 airlock doors to theatre (3 m) Self-closing Closure of plastic swinging doors to recovery 86 room (3 m) 85 Plastic kidney dish falling onto floor (2 m) 85 Patient trolley sides lowered (2 m) 85 Patient trolley sides raised (2 m) 80-85 stainless steel bowls (2 m) Clanging 75-80 Sucker in use by surgeon (1 m) 75-80 Sucking out pharynx (anaesthetist) (1 m) 80 Oxygen supply alarm (3 m) 78 Oscillating saw opening chest (1 m) 75 Scavenger system for anaesthetic gases (1 m) 75 Instrument trolley wheeled into theatre (2 m) 75 instruments from m) Unwrapping paper (2 75 Electrocardiogram monitor alarm (1 m) 74 Ventilator disconnection alarm (1 m) 73 Sucker (on operating table) not being used (1 m) 70 intercom on theatre (3 m) Incoming speech 65 Ventilator (2 m) 65 machine (3 m) Diathermy 62 Intercom "incoming call" alert (3 m) 60 Normal speech between theatre staff (1 m) 53 monitor Automatic blood pressure (inflating) (1 m) Intermittent calf compression machine (inflating) (1 m) 52
TABLE II-SOUND LEVELS OF COMMON NOISES
The loudest noises were usually recorded during the preparation period of the operation. During surgery the principal sources of continuous noise were the sucker and the ventilator: noise levels were much higher than levels of normal speech between staff. Main sources of intermittent noise included the diathermy machine, anaesthetic alarms, and the intercom. Only for 1 % of the time did sound levels exceed what is regarded as a ’moderate’ noise level (table II). The Leq of 51 dB(A) falls into the quiet range.
regarded as being noisy only when it is unwanted objectionable, interferes with work tasks, impairs verbal commmunication, or prevents sleep. It is important to recognise that these assessments are subjective and therefore differ between observers. For example, loud discotheque music at a party may be regarded as noise by an individual who is trying to sleep or study, but not by the person who is attending the party. Although the characteristics of a noise-eg, its level, frequency distribution, time variation--can easily be assessed, the application and interpretation of this Sound is
information is more difficult. Because the human ear does not process sound equally across the frequency spectrum, a weighting system, the "A" scale, has been devised. This scale closely correlates with noise nuisance and hazard assessment for human beings.6 Certain points should be considered in the study and interpretation of noise levels. Sound is measured on a logarithmic scale, which means that additional sounds of similar intensity will not greatly increase the total sound level. A sudden or impact noise with a level as little as 30 dB above the background level (eg, a dropped instrument) is likely to cause a "startle response" and subsequent stress reaction. This can be important if the task being done requires much vigilance or concentration, as, for example, during critical periods of a surgical operation.7 The startle response produces complex physiological reactions typically associated with stress, including pupil dilation, increased adrenalin secretion, and elevation of blood pressure .3,1 ,I,I The extent of these physiological reactions tends to increase when the noise is intense, when it is aperiodic, or when it is uncontrollable.S The background noise level in the operating theatre in our study was low enough to make no substantial contribution to the noise measured in the theatre during periods of activity. This level is within the recommended levels for a satisfactory working environment; the Standards Association of Australia recommends that background noise levels should not exceed 30 dB(A).lo,l1 The equivalent sound pressure levels which reflect the overall sound levels during the recorded operation, were also acceptably low (table I). However, the effect of noise on performance depends not only on its level and the stress tolerance of the individual, but also on the complexity of the task and the type of noise. Two features of the type of noise are important-namely, whether it is predictable and whether it is controllable. Predictable noises are continuous or periodic, and unpredictable ones are discontinuous or episodic; controllable noises can be terminated at will, whereas uncontrollable ones cannot. Even high level continuous noises (90-120 dB) have no detrimental effects on the performance of simple motor or mental tasks. 12 14 However, noises of lesser amplitude, especially when they are unpredictable, uncontrollable, or both, can interfere
TABLE III-PREFERRED SPEECH INTERFERENCE LEVELS (PSILs) FOR STEADY CONTINUOUS NOISES AT WHICH RELIABLE COMMUNICATION IS BARELY POSSIBLE
" Adapted from Beranek These PSILs apply only to individuals wIth completely normal hearing Even hearing impairments will lower the PSILs substantially
for male/female voices
substantially with the performance of complex tasks. 13 Furthermore, noise has more than just immediate effects on performance, which is impaired for a long time after the noise has stopped.6,7,12 Kestin et al15 found that with five commonly used anaesthetic monitoring devices 75 % of the alarms that sounded were spurious, with only 3% indicating risk to the patient: an average of 10 alarms sounded per patient, with a mean frequency of 1 alarm every 4-5 min. Such intermittent intrusive noises are unpredictable and to an extent uncontrollable, and therefore are likely to greatly interfere with the concentration and performance of the surgeon. The peak sound levels of 75-85 dB(A) recorded in the theatre in our study could certainly be expected to interfere with the concentration of staff doing complex tasks. Predictable noises (the most common being the ventilator and the sucker) may also create distraction and impair performance, but to a lesser extent. Individual responses are also important: a noise that aggravates one person may not be as intrusive to another individual. Background conversation interferes with performance much more than does noise that is not discernible as conversation.16,17 Members of a surgical team may be easily distracted by conversations between other members of the team. Background music played in the theatre at low volume so that communication is not impaired may be extremely beneficial by masking other sounds (especially background
conversation). Perhaps the most serious effect of excessive noise in the operating theatre is that it impairs and sometimes prevents reliable communication. That communication in the theatre is clearly understood if procedures are to be done efficiently and safely is essential. It is also noteworthy that the
comprehension of verbal communication may be impaired even at
noise levels which do
intelligibility.14 When a number of distinct auditory signals are presented simultaneously, it is often difficult for the human ear to distinguish or discriminate between them. This phenomenon, known as masking, accounts for the difficulty experienced in hearing others talk in the presence of loud background noise.12 The reliability of oral communication can be assessed by calculation of preferred speech interference levels (PSILs), 10,1-7,18 which are the arithmetic averages of the sound pressure levels of the noise (dB, linear scale) in three octave bands centred on 500, 1000, and 2000 Hz. Sound levels that just permit reliable conversation are shown in table II. Our intraoperative data suggest that communication difficulties are unlikely at 0-6 m separation, which is the approximate distance between surgeon and assistant, or even at 1-8 m, although the
data are averaged over 5 min. Individual peak noises with levels of 70-80 dB(A) will greatly interfere with communication, but these will be hidden in the equivalent level figures. During the high noise levels of the preparation for an operation the PSILs are often exceeded. Even when voices are raised, communication is often hampered and unsatisfactory. This has important implications for safety because initial counting of instruments, sponges, swabs, and needles is done during this period and any impairment of communication increases the likelihood of counting discrepancies. Furthermore, a comparison of noise levels during the operation in our study with PSILs (table ill) shows that reliable communication between any two team members may be possible only with shouting. Equipment that is not needed for immediate use should be turned off or an alternative method could be used—eg, a sponge or swab, instead of a sucker. Extraneous noise can become an especially serious problem for a conscious patient during local or regional anaesthesia. An operation is stressful for most patients, and added stress and anxiety should be avoided by keeping noise to a minimum. Sudden loud noises not only raise stress levels for the patient, but also may cause a startle response with movement of that part of the body on which the surgery is being performed. Earplugs, soothing background music, or music played through headphones may be beneficial to reduce to a minimum noise-induced stress for these patients. We recommend the following to reduce the noise pollution in operating theatres: 1. The patient should not be in theatre during the preparation of the operation. 2. Patient and instrument trolleys should be designed to reduce to a minimum the noise that they cause in the operating theatre. 3. Use of softer paper or other material for wrapping instruments for sterilisation should be investigated. 4. Plastic bowls and trays should be used whenever
possible. 5. Ear plugs or music- from headphone sets should be offered to patients having local or regional anaesthesia to reduce anxiety; the use of background music both to calm patients waiting in anaesthetic rooms and to mask anxiety-provoking sounds coming from the operating theatre should also be considered. 6. Deliberate masking of other sounds in the operating theatre by soft background music should be considered. 7. Suckers should be used as little as possible and turned off completely when not required. 8. Anaesthetic monitors and alarms should produce signals that will be noticed by the anaesthetist but that should not be intrusive and cause distraction to other staff. A warning should always be given before alarms are tested. 9. Whether paging devices, intercoms, and telephones in operating theatres are needed must be carefully assessed because of their potential to distract staff and disturb conscious patients. 10. Noise pollution should be considered in the design of new operating theatres (eg, installation of sound insulation between scrub-up and sterilisation areas and the theatre itself, avoiding the use of hard, soundreflective ceilings and walks). 11. New equipment for use in an operating theatre should be chosen carefully with respect to potential noise.
We thank Mr Marsyas Sherman and Mr Ken Mikl from the New South Wales Department of Industrial Relations and Employment, division of occupational health, Lidcombe for their assistance with recording and analysis of data. We also thank Ms Karen Hynes and Ms Paula Mohacsi for their valuable contributions to the preparation of the manuscript.
Shapiro RA, Baland T. Noise in the operating room. N Engl J Med 1972;
287: 1236-37. 2. Mori H, Murata H. A study of noise in operating room. Jap J Anaesthesiol 1979; 10: 1102-06. 3. Falk SA, Woods NF. Hospital noise-levels and potential health hazards. N Engl J Med 1973; 289: 774-81. 4. Davies JM, Ewen A, Cuppage A, Gilbert D, Winkelaar R. Noise levels in the operating rooms—a comparison of Canada and England. Anaesthesia Intensive Care 1989; 17: 98-99. 5. Cromer AH. Physics for the life sciences. New York: McGraw Hill, 1974. 6. Walker JG. Handbook of noise assessment. May DN, ed. New York: Van Nostrard Reinhold, 1975; 7: 185-94. 7. Fisher JD, Bell PA, Baum A. Environmental psychology. 2nd ed. New York: Hold, Reinhart and Winton, 1984.
8. Holahan CJ. Environmental psychology. New York: Random House, 1982. 9. Aitken RJ. Quantitative noise analysis in a modern hospital. Arch Environ Health 1982; 37: 361-64. 10. Acoustics: methods of assessing and predicting speech privacy and speech intelligibility. Australian Standard 2822-1977. Standards Association of Australia, 1977. 11. Ambient sound levels for areas of occupancy within buildings. Australian Standard. 2107-1977 Standards Association of Australia, 1977. 12. Glass DC, Singer JE. Urban stress. New York: Academic Press, 1972. 13. Kryter KD. The effects of noise on man. New York: Academic Press, 1970. 14. Baum A, Fisher J, Singer J. Social psychology. New York: Random House, 1985. 15. Kestin IG, Blaine R, Miller DO, Charles H, Lockhart MD. Auditory alarms during anaesthesia monitoring. Anaesthesiology 1988; 69: 106-09. 16. O’Szewski DA, Rolton J, Soler EA. Conversation, conglomerate noise and behavioural after effects. Paper presented at a meeting of the Mid Western Psychological Association, Chicago, 1976. 17. Hockey GRJ. Effects of noise on human work efficiency. In: May DN, ed. "Handbook of Noise Assessment. New York: Van Nostrard Reinhold: 1978: 335-69. 18. Beranek LL. Noise and vibration control. New York: McGraw Hill, 1971: 554-603.
No-scalpel vasectomy at the King’s birthday vasectomy festival
No-scalpel vasectomy was developed to increase acceptability of vasectomy by elimination of the fear of the incision. Although this method has been used for over 8000 000 men, the technique is largely unknown in developed countries. During the King’s birthday vasectomy festival no-scalpel vasectomy was compared with standard incisional vasectomy in 1203 patients. An average of 57 procedures per day could be done by each physician with the no-scalpel method, compared to 33 procedures with the standard method (p