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Noise suppressing features reduce auditory sensory perception: Study

25 May 2021

  • Headphone-wearing pedestrians, joggers, cyclists at risk of accidents

By Ruwan Laknath Jayakody   Pedestrians, joggers, and cyclists who utilise headphones while they are on the road and are thereby rendered unable to hear the sounds of vehicle horns and to receive auditory input from vehicles, are more at risk of facing a road traffic accident than those among them who do not, a study noted. The study further noted that the noise suppressing features of headphones contribute to reducing the auditory senses of pedestrians and recommends modifications in headphones in order to resolve this issue. These findings were made by J.K.D.R. Jayasekara (attached to the Department of Information Technology [IT] of the CINEC Campus) and D. Dhammearatchi (attached to the Millennium Drive, IT Park) in a research article titled “Accident Proof Headphones: An Analytical Research on How Smart Headphones Could Reduce Road Fatalities”, which was published recently in the CINEC Academic Journal. Deaths and injuries among headphone-wearing pedestrians have, Jayasekara and Dhammearatchi noted, rapidly increased over the years. In addition to pedestrians, many cyclists and joggers too, the duo pointed out, face such accidents. They cite the case of the US where the numbers of related fatalities and injuries have tripled during the past seven years. R. Lichenstein, D.C. Smith, J.L. Ambrose, and L.A. Moody noted in “Headphone use and pedestrian injury and death in the US: 2004-2011” (2012), that 70% of such accidents resulted in the pedestrian’s death, that over one-third of such fatalities were of those below 18 years of age while the majority (approximately two-thirds) were of those less than 30 years, and also that the majority (roughly 90% of such collisions) occurred in urban areas or large cities.
  1. Williams' “Noise exposure levels from personal stereo use” (2005) which compared the sound level of music being played through a headphone of a wearer with the noise level of various background environments, found that there was a difference of almost 13 decibels (dB – measures the sound intensity and degree of loudness) between the two (average 86.1 dBs in the headphones and 73.2 dBs being the typical noise level in the various background environments). Since there is a noise cancellation of 27.4 dBs provided by an average pair of headphones, any noises that the pedestrian should be able to hear will be clouded or simply unheard, the researchers note.
This can in turn prove to be quite dangerous for pedestrians, joggers, and cyclists who are deprived of their basic auditory senses, Jayasekara and Dhammearatchi added, noting that this kind of behaviour, especially when exhibited in busy urban street areas, can prove to be fatal for the listener. Moreover, the nature of the accident, the duo observe, might not always be a head-on collision with a vehicle, and in this regard, cited an incident in 2016 where a cyclist who was using headphones and had entered a roundabout, having suddenly noticed a vehicle exiting the roundabout at the same time, had panicked at the sudden sight of the vehicle, and fallen from the cycle onto the sidewalk, resulting in the instantaneous fracture of her skull and spinal cord. The researchers also point to studies which have shown that there has been some sort of warning or indication of such an incident being about to occur before most such pedestrian fatalities take place. A pedestrian who is not using headphones would, Jayasekara and Dhammearatchi explain, have a higher chance of hearing an approaching vehicle, the noise of brakes being applied, or the honks from a car while headphone users might not hear or even see any of these danger cues due to unintentional blindness (inattentional blindness is described by D. Simons in “Failures of awareness: The case of inattentional blindness” as the inability to notice various objects or events when one's attention is directed elsewhere) caused by a sensory overload. According to the statistics of “Global headphones and headsets sales 2017/Statista”, the use of headphones or earphones has increased drastically on a large scale every year and will further increase with new improvements being made to modern technologies. The main purpose of the usage of headphones or earphones is, according to the “Global earphones and headphones market size report, 2020-2027”, entertainment (to listen to music). The results of “905 Distracted walking among teens and pre-teens in the US and China: analysis of observations” (2016) by P. Gautam, M. Cui, F. Wang, K. Rosenthal, and R. Ferguson and £Plight of the distracted pedestrian: A research synthesis and meta-analysis of mobile phone use on crossing behaviour” (2020) by S.M. Simmons, J.K. Caird, A. Ta, F. Sterzer, and B.E. Hagel, showed 39% being distracted due to headphones in the US and 42% in China. Wearing a pair of headphones will automatically cut off about 15 to 20 dBs of surrounding noise from the listener’s ears while additional noise reduction of around 20 dBs is provided by modern-day headphones, Jayasekara and Dhammearatchi observe. They note based on data gathered by leading companies in the audio industry that the majority prefer to use headphones with noise cancellation and noise reduction capabilities over normal ones. As explained by the duo, although these properties such as noise cancellation, custom fitting, and in-ear headphones are beneficial for most of the users in noisy environments, it can, however, lead to devastating repercussions for pedestrians on busy roads. In “Keeping ‘one ear open’: The dangers of earbuds and headphones”, it was noted that in the majority of such cases, a warning noise was heard beforehand, where in the case of train accidents, even though trains have been known to repeatedly blast their horns in order to warn pedestrians, this has been ineffectual. In “Smart Headphones/Omdia/Tractica”, it was observed that although many present-day smart headphones are equipped with a wide range of advanced features such as language translation, audio enhancement, fitness tracking, and personal assistants, none have been developed to ensure a pedestrian’s, cyclist’s, or jogger’s safety. According to “Audio analytic/37 million people at risk of ‘distraction danger’ when wearing headphones” (2019), in 2018, 37 million Americans had felt that they were more exposed to danger when wearing headphones or earphones while walking, jogging, or cycling. This research by Jayasekara and Dhammearatchi was conducted using primary data and quantitative secondary data, and analysed data gathered from major companies which manufacture the most in-demand headphones with noise isolating (passive isolation where noise suppression takes place due to the physical design of the earbuds or the material of the headphones, and active noise cancellation where scientific technology is used to neutralise sounds which infiltrate the headphones) attributes, analysed and compared the amount of background noise cut off by each headphone, and measured the noise level and sound intensity of car honks at fixed distances for three seconds to clarify whether headphone users were able to hear them in a fairly moderately busy street environment. Data was gathered to calculate the mean noise isolation for the bass, mid, and treble ranges separately for five headphones, each from different brands which had the highest ratings for the best noise-cancellation features. The headphones considered in the study were the over-ear type with the closed back enclosure. The lowest mean noise suppression belonged to the bass range category at 20.56 dBs while the treble range had the highest suppression level of 37.6 dB and the mid range had a suppression of 24.03 dBs. The overall mean noise cancellation produced by a pair of headphones was computed as being at 27.4 dB. The sound was measured using a noise meter app with pre calibrated measurements to assess the sound pressure level. It was clearly observed in the study that the longer that the horn is sounded, the intensity increases swiftly. It was found that the average sound intensity of a car horn is at the highest when the pedestrian is one metre distance away from the vehicle. The intensity gradually decreases as the pedestrian moves further away from the vehicle but still remains above 90 dBs. The average intensity, it was also found, varies from vehicle to vehicle since horns used by heavy vehicles have a much larger intensity than that of others. Discussing the results, Jayasekara and Dhammearatchi observed that there is a very low chance of a pedestrian who is wearing headphones hearing a noise before an accident is about to occur. The pedestrian might therefore be having and experiencing “inattentional blindness”, the researchers note, especially if he or she is listening to music at a high volume level. The results also show that it is more feasible and easier to detect vehicle honks in a busy street environment rather than detecting car tyre or engine sounds, as they can be heard clearly over other noises. The perception reaction time of a driver responding to the unexpected sight of a pedestrian in front of the vehicle is of a duration ranging between two and five seconds as noted by the American Association of State Highway Officials’ “A Policy on the Design of Urban Highways and Arterial Streets”, whereas the median reaction time for a pedestrian, according to N. Waldau-Drexler's “Pedestrian and evacuation dynamics 2005” (2007), is 0.3 seconds. However, Jayasekara and Dhammearatchi observe that even though the reaction speed of a normal pedestrian is quite high, there will be a substantial delay in this speed when it comes to a pedestrian wearing a headphone. Furthermore, as explained by the duo, the sudden reactions of a driver in a vehicle travelling at high speed will result in the driver losing control of the vehicle and he or she will most likely be over-applying the brakes where the after-effect usually produces a noise such as that of a screeching sound. Again, while a normal bystander would hear such noises even before seeing the vehicle, which will in turn provide them with a longer time limit to secure themselves, this will, the researchers mention, not be the case for a pedestrian wearing headphones, especially if his or her back is turned to the vehicle. As a possible solution to overcome all of these issues, the duo suggested the development of cost-effective and user-friendly smart headphones with the technology to alert the wearer of any forewarnings regarding the danger of using embedded systems. "Miniature microphones added to the headset externally could be able to record the noises in the environment, and these microphones in turn should be placed in such a manner that the noise detected will be balanced on both the left and right sides of the headphone. Furthermore, depending on the direction of the approaching vehicle or any such imminent danger, the headphone should be equipped to alert the user with a beep or a signal on that specific side of the ear (either left or right). Sensors, as pointed out by J. Majchrzak, M. Michalski, and G. Wiczynski in “Distance estimation with a long-range ultra-sonic sensor system” (2009) could be used to estimate the distance between the pedestrian and an incoming vehicle. The microphones which are situated externally on the pair of headphones will be able to transfer the data to be analysed in real time. Since almost all headphone wearers travelling on the road use a headphone with the assistance of a smart phone, it would be convenient for the user to have an installable application (app) which can be used to display more information regarding his or her environment and be used to keep the user constantly aware of his or her surroundings. Therefore, with the revenue generated by the sale of smart headphones increasing rapidly each year, it would be a smart move to develop headphones which aid in the listener’s safety, especially with the modern technological concepts used in headphones today.


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