Equal Energy Principle Research Articles

Attention to rattles and a non-equal-energy model are required for proper sonic boom assessment

This paper is concerned with the assessment of community response to sonic booms or blasts. It summarizes and analyzes the totality of results from studies in the English language that used real booms or blasts, with subjects in real buildings. In acoustics, we are accustomed to noise sources operating in accordance with the equal-energy principle (a 1 dB increase in amplitude is equivalent to a 1 dB increase in duration). The results show that rattles are the most important attribute contributing to the annoyance engendered by sonic booms/blasts, and that the process is not equal-energy. Rather, the equivalent annoyance generated by a change of 1 dB in the C-weighted boom or blast amplitude is equal to about a 1.5 to 2 dB change in the boom or blast duration where the exchange rate is defined to be 1 over these changes in duration, 0.67 and 0.5, respectively. The exchange rates found in several sonic boom/blast noise studies are given, and as an example, the exchange rate for the historical Oklahoma City study is calculated. The conclusions from the Long-Term Sonic Boom Noise Environments study are examined in relation to the range of exchange rates found in other boom/blast studies.

The trade-off between pulse duration and power in optical excitation of midbrain dopamine neurons approximates Bloch’s law

Optogenetic experiments reveal functional roles of specific neurons. However, functional inferences have been limited by widespread adoption of a restricted set of stimulation parameters. Broader exploration of the parameter space can deepen insight into the mapping between selective neural activity and behavior. In this way, characteristics of the activated neural circuit, such as temporal integration, can be inferred. Our objective was to determine whether an equal-energy principle accounts for the interaction of pulse duration and optical power in optogenetic excitation. Six male TH::Cre rats worked for optogenetic (ChannelRhodopsin-2) stimulation of VTA dopamine neurons. We used a within-subject design to describe the trade-off between pulse duration and optical power in determining reward seeking. Parameters were customized for each subject based on behavioral effectiveness. Within a useful range of powers (~12.6–31.6 mW) the product of optical power and pulse duration required to produce a given level of reward seeking was roughly constant. Such reciprocity is consistent with Bloch’s law, which posits an equal-energy principle of temporal summation over short durations in human vision. The trade-off between pulse duration and power broke down at higher powers. Thus, optical power and duration can be adjusted reciprocally for brief durations and lower powers, and power can be substituted for pulse duration to scale the region of excitation in behavioral optogenetic experiments. The findings demonstrate the utility of within-subject and trade-off designs in optogenetics and of parameter adjustment based on functional endpoints instead of physical properties of the stimulation.

Electrofusion by a bipolar pulsed electric field: Increased cell fusion efficiency for monoclonal antibody production

The excessive cell death rate caused by electrofusion with unipolar pulses (UPs) has been a bottleneck to increasing cell fusion efficiency in monoclonal antibody technology. Several studies have confirmed that compared with UPs, bipolar pulses (BPs) with microsecond pulse widths can increase electropermeabilization while reducing cell death. Given these characteristics, BPs were used to increase cell fusion efficiency in this study. Cell staining and hybridoma culture experiments were performed using SP2/0 mouse myeloma cells and lymphocytes. Based on the equal energy principle, UPs and BPs were delivered to electrodes at a distance of 3.81 mm, with electric field intensities ranging from 2 kV/cm to 3 kV/cm and pulse duration of 40 μs for the UPs and 20–20 μs for the BPs. The results of cell staining experiments showed that cell fusion efficiency was 3-fold greater with BPs than with UPs. Similarly, the results of the hybridoma culture experiments showed that the hybridoma yields were 0.26‰ and 0.23‰ (2.5 kV/cm and 3 kV/cm, respectively) in the UP groups and increased to 0.46‰ and 0.35‰ in the BP groups. Taken together, the results show that the efficiency of heterologous cell fusion can be greatly increased if BPs are used instead of the commonly applied UPs. This study may provide a promising method for monoclonal antibody technology.

Occupational Noise Exposure of Traffic Enforcers in Selected Streets in the City of Manila

Objective. The study aimed to evaluate the sound pressure levels of selected traffic enforcer sites in the City of Manila.
 Methods. A Brüel & Kjær Integrating Sound Level Meter type 2225 was used to measure sound pressure levels in dB(A) to estimate personal noise exposure of traffic enforcers designated at Quezon Boulevard near Quiapo Church and Recto – Rizal Avenue on a weekday and a weekend. Graphs were generated while appropriate measures were calculated for the noise exposure levels. The mean exposure levels were compared with the Philippine Occupational Safety and Health standards by computing the corresponding permissible exposure limit for each work shift using the Equal Energy Principle.17
 Results. Noise exposure levels at Quezon Boulevard ranged from 75.0 dB(A) to 91.5 dB(A) with mean noise exposure level of 84.3 ± 3.7 dB(A) and 82.5 ± 2.6 dB(A) for the weekday AM and PM shift, respectively. The mean noise exposure level at Quezon Boulevard for the weekend AM shift was 82.4 ± 2.6, whereas 80.4 ± 2.8 for the PM shift. The noise exposure levels at Recto – Rizal Avenue ranged from 81.5 dB(A) to 99.3 dB(A) with mean noise exposure level of 86.7 ± 2.6 dB(A) and 86.0 ± 2.1 dB(A) for the weekday AM and PM shift, respectively. The mean noise exposure level at Recto – Rizal Avenue for the weekend AM shift was 86.7 ± 2.3, whereas 89.0 ± 4.0 for the PM shift.
 Conclusion. The study showed that traffic enforcers designated at Quezon Boulevard and Recto – Rizal Avenue are exposed to noise levels that do not exceed the Philippine Occupational Safety and Health standards.

Study on design and simulation analysis of the double horse-head pumping unit based on the compound balance structure

Double horse-head pumping unit, being one of the most classical mechanical equipment, has high efficiency and good balance ability during the oil extraction owing to its horse-head structure connecting with the rod by the steel wire rope. But its characteristic of energy consumption reduction is limited because of the motor torque fluctuation and negative torque appearing while the pumping unit is working in the upstroke and downstroke. The compound balance design is applied to the double horse-head pumping unit by the crank balance and walking beam balance, which is completed by the equal energy principle during the up and down circulation of the oil suction unit. The finite element model of the whole equipment is built, and the simulation analysis is completed by the software ADAMS, under the conditions of the compound balance and that of the crank balance. The output torque of the crank, the forces from the back horse-head rope, and the connection pin are calculated. From the viewpoint of system design to compare with the traditional crank balance pumping unit, the compound balance design can reduce the torque fluctuation greatly, decrease the forces of steel wire rope connecting with the back horse-head, and get rid of the structure problems from the traditional pumping unit. The stress test of the double horse-head pumping unit designed by the compound balance method is completed in the oilfields. It has proved the correctness and reasonability of the compound balance design. The methodology of the compound balance design is helpful in improving the work efficiency and reliability and bringing about better abilities of energy consumption reduction for the pumping unit during its work circulation.

A snapshot of young adults’ noise exposure reveals evidence of ‘Binge Listening’

There have been several previous studies into daily noise exposure levels in modern urban communities, which typically report mean noise exposure levels (LAeq) for adults between 73 and 79dB. In this study, rather than focus on group mean exposures across a wide age range, individual patterns of noise exposure over 4- and 5-day periods were examined in a group of 45 young adults aged 18–35years. The main objective of the study was to determine the extent to which young adults exhibit a ‘binge listening’ pattern of noise exposure, i.e., high weekend leisure noise vs. low weekday work noise exposure. A secondary objective was to identify the types of activities that generate the highest noise exposures. The results showed that although most participants (60%) were exposed to low daily noise levels, 33% of participants exhibited a ‘binge listening’ exposure pattern characterized by one or two high-noise days, usually a Friday, Saturday or Sunday, preceded or followed by much quieter days. The most notable high-noise activities were playing an instrument solo or in a band; attending a nightclub; and attending a pop concert, each of which recorded average noise levels greater than 100dB. Future research is needed to determine whether ‘binge listening’ is more or less harmful than the chronic exposure presupposed in traditional risk models, however, under the equal-energy principle, repeated ‘binge’ noise exposures from weekend visits to nightclubs, live music events and other high-noise events represent a significant risk to long-term hearing health.

SIG 8 Perspectives Vol. 12, No. 1, December 2011

SIG 8 Perspectives Vol. 12, No. 1, December 2011

Noise and Public Health

In this article, I provide an overview of current issues and resources related to noise and public health for speech and hearing professionals and their clients. For context, some background information is given, including a brief description of the equal energy principle and the measurement of sound. Regulatory agencies and guidelines for recreational versus workplace noise are differentiated. Some common noisy recreational activities are surveyed and resources for education about hearing loss prevention are listed. Auditory as well as non-auditory health effects of noise are described and explored.

The effects of tone exposure on the inner ear functions in the guinea pig: impact tone vs. steady state tone.

The damage-risk criterion (DRC) for hearing supposes that sound exposure with equal energy implies equal risk for noise-induced hearing loss (NIHL). We measured cochlear microphonics (CM), compound action potential (CAP), endocochlear potential (EP) and K+ ion concentration in the scala media, to see if the same level of Leq24h (impact tone and steady state tone) induced the same physiological changes in the inner ear function or not. Regarding the equal energy principle (EEP), we also examined if the EEP is appropriate or not at exposure of moderate level tone. We also checked how the time interval between impact tones affects or not the inner ear functions at the same Leq24h tone exposure. Therefore we used exposure at 1 pulse/second or 1 pulse/3 seconds and steady state tone exposure at Leq24h=90, 85 and 80 dB. The results are the following. Both steady state and impact tone exposure causes change of the electrophysiological data. First, CM maximum output voltage after exposure to impact tone of 115 dB (Leq24h=90 dB) was lower than after exposure to a 8 kHz steady state tone of 90 dB. CAP threshold (below 10 microV) obtained after the 115 and 110 dB exposure of impact tone were 5-10 dB higher than that of steady state tone of 90 dB. The negative EP induced by impact tone exposures showed the same tendency as the CM experiments. Having more frequent pulses (1 pulse/second vs. to 1 pulse/3 seconds) showed more inhibition. The K+ concentration time course remained similar to the control when the Leq24h was low (80 dB). Impact tone exposure induced stronger effects to the inner ear at exposure of moderate level tone than that of steady state tone of Leq24h.

Investigation of intermittency in the noise exposure pattern of longwall coal miners

It is generally recognized that intermittent exposures to noise are less hazardous than continuous exposures with the same energy. This effect has been accounted for in the USA with the use of a 5-dB exchange rate, instead of the 3-dB rate associated with the equal energy principle. However, the appropriateness of the 5-dB exchange rate for assessing the risk of noise exposures in mining has never been examined closely. The authors have previously reported the results of a worker noise exposure survey conducted at six longwall coal mines [R. C. Bartholomae and J. A. Burks, Proceedings: NOISE-CON ’94, 1017–1022 (1994)]; the time-resolved dosimeter data from that study were reanalyzed to determine if the noise exposure pattern of longwall miners can be categorized as intermittent. For this purpose effective quiet is defined to be a period of time in which the sound level is less than 75 dBA [W. Melnick, J. Acoust. Soc. Am. 90, 147–154 (1991)] for 10 s or longer [K. D. Kryter, The Effects of Noise of Man (1985), p. 273]. It is found that the miners experience an average of 125 periods of effective quiet and an average total quiet time of 1.7 h on a daily basis.

Prolonged exposure to gunfire noise among professional soldiers.

The aim of the study was a retrospective assessment of the exposure of professional soldiers to impulse noise from gunfire. A questionnaire on noise exposure and use of hearing protectors was administered to a stratified random sample of 699 army officers (mean age 39.8 years) with an average of 18 years of exposure to shooting noise. For a comparison of the number of shots from different weapons, the peak sound pressure levels of shots were adjusted in relation to one pistol shot according to the equal energy principle. Total exposure time was estimated with the equal energy principle, the number of shots from different weapons, the energy levels of different shots, the effectiveness of hearing protection, and the distance from the noise source being taken into account. Rifles, shotguns, and pistols were the predominant exposure sources. Impulse noise exposure averaged 164,183 shots from different weapons. After adjustment to the energy level of one pistol shot, the average was 78,000 personally fired shots. The total shooting noise exposure averaged 218,000 adjusted shots. Translated into exposure to steady noise of 85 dB(A) for 40 h a week, the exposure to noise from personally fired shots equaled an exposure time of 22.0 years and the total exposure averaged 61.0 years. The heaviest exposure occurred during the first 10-15 years of the men's careers. Exposure to gunfire noise among professional soldiers is high enough to cause severe hearing deterioration already at early career stages if effective hearing protectors are not worn at all times on shooting occasions.

Qualitative and quantitative changes in the guinea pig organ of Corti after pure tone acoustic overstimulation

A direct relationship between delivered sound energy and morphological overstimulation has been formulated in the so-called equal energy principle. The validity of this principle was systematically tested by studying the effects of acoustic overstimulation on the guinea pig cochlea by means of scanning electron microscopy (SEM) and light microscopy (LM) techniques. The animals in the present study were exposed to 3.85 kHz pure tones of various durations and intensities and allowed a recovery period of 4 weeks before the morphological changes in the cochlea were assessed. A 4-grade scale was devised in order to achieve a qualitative as well as a quantitative SEM evaluation of the cochlear damage. The results of the examinations by LM and SEM were compared and analysed statistically. No significant difference was observed between groups of animals exposed to a sound energy of 9.4 and 37.5 Pa 2 · h, irrespective of sound intensity (114 or 120 dB SPL). Groups of animals exposed to a higher energy level (150 Pa 2 · h) differed significantly from those exposed to higher and also lower sound energy levels. Groups exposed to different intensities (108, 114 and 120 dB SPL) did not differ significantly within this energy level.

Noise-induced cochlear damage assessed using electrophysiological and morphological criteria: an examination of the equal energy principle.

Cochlear damage immediately following exposure to continuous pure tones of varying intensity and duration was assessed in anaesthetized guinea pigs. Indices of damage used were elevation of N1 thresholds and severity of swelling of the afferent dendrites beneath the inner hair cell. The results were not wholly consistent with the assumptions of the equal energy principle. Longer duration exposures resulted in greater N1 threshold elevation and more severe swelling of dendrites than short exposures of the same total energy.

Judged acceptability of noise exposure during television viewing

Noise masking of television audio signals by flyovers is the most frequently mentioned problem of airport neighbors. This problem was studied in the laboratory using artificial noise. Three studies varied the intensity, duration, and rate (noises per hour) of the noises. Acceptability was found to approximate a logarithmic function of noise energy for changes in intensity, duration, and rate. Thus, the equal-energy principle, which has been generally observed in abstract psychometric experiments, was confirmed in this more realistic and representative task. A fourth study showed aircraft-flyover recordings to be more acceptable than artificial noises even though they had equivalent peak levels and masking durations. This difference can also be explained by the equal-energy principle, since the flyovers had lower average (or integrated) energy.

Studies in hearing conservation

This paper together with two companion papers comprise a review of the greater part of the research on hearing conservation carried out over the past ten years at the Institute of Sound and Vibration Research of the University of Southampton. The research described in this paper includes studies of temporary threshold shift from exposure to impulse noise and to mixtures of continuous and impulse noises, the establishment of damage risk criteria for gunfire and other types of impulse noise, the hazards to hearing from ultrasound and studies on the measurement of the attenuation of hearing protection. The current state of ideas and research in these aspects of hearing conservation are discussed together with indications of possible future trends and requirements. Recent work on the extension of the damage risk criteria studies to the establishment of an equal energy principle for hearing damage for all types of noise is described in the first of the two companion papers, by Rice and Martin; the second companion paper, by Coles and Martin, is a review of certain medico-legal aspects of hearing conservation.