In the present study, the noise level data from Ahmedabad observed consistently high levels across different times of the day. The mean noise levels recorded were 79.88 ± 2.84 dB during the day, 74.76 ± 1.75 dB at night, and 61.47 ± 1.97 dB during the late-night hours (1 AM-6 AM). The maximum noise levels reached 84.96 dB at during the day, 77.9 dB at night, and 64.92 dB during late-night hours (Fig. 2). The minimum noise levels recorded were 75 dB during the day, 72.03 dB at night, and 58.03 dB during late-night hours. These findings show that Ahmedabad's noise levels were about the same as, or marginally greater than, those seen in other major Indian cities as compared to other research studies. A study conducted in Delhi by Chauhan et al. (2010) recorded that the average noise levels during the day in commercial and industrial sectors ranged from 75 to 80 dB, which was similar to the values recorded in Ahmedabad. Goswami & Swain (2017) found that the average noise levels in commercial areas of Bhubaneswar throughout the day were approximately 75 dB, which was slightly lower than the levels seen in Ahmedabad. A study carried out in Mumbai by Vijay et al. (2013) likewise showed high noise levels, with daytime averages above 80 dB in heavily traveled areas, which was in line with the values observed in Ahmedabad. This indicated that Ahmedabad's noise pollution exceeded other large Indian cities noted for their high levels of urban noise pollution. Comparing these findings with research conducted in other countries, the noise levels in Ahmedabad were also consistent with or higher than those recorded in other urban regions around the world. For instance, research in São Paulo, Brazil, revealed typical daytime noise levels in commercial districts to be about 75 to 82 dB, close to the values documented in Ahmedabad (de Paiva Vianna et al., 2015). In contrast, research in London revealed lower average noise levels, around 65 to 70 dB during the day in commercial zones (Gulliver & Briggs, 2011), emphasizing that Ahmedabad’s noise pollution is substantially greater than in several European cities.
Residential Areas
The present study revealed significant variations in noise levels in residential areas during different times of the day. The mean noise levels recorded were 79.83 ± 2.66 dB during the day, 74.85 ± 1.70 dB at night, and 61.68 ± 1.90 dB during the late-night hours (1 AM-6 AM). The maximum noise level recorded during the day was 84.9 dB at the Bhairavnath bus stand, while the minimum was 75 dB at the Sardar Patel bus stand, respectivily. At night, the noise levels ranged between 72.03 dB (Medical college) and 77.9 dB (Manekbaug Cross Road). During the late-night hours, the noise levels were notably lower, with a maximum of 64.85 dB at the Ajeshwari Society - Bus stop and a minimum of 58.14 dB at Zundal Circle. The higher noise level during the daytime witnessed to more traffic and bus stands near the residential area (Fig. 3). These noise levels were considerably higher than those reported in other studies focusing on residential areas. For instance, Khan & Lone (2017) observed noise levels in residential areas of Delhi that exceeded prescribed standards by about 25 dB, reaching up to 67 dB. This is still lower than the average day and night noise levels in the current study. Similarly, Ranpise & Tandel (2021) recorded noise levels in a silent zone of Surat city, Western India, at 79 dB, which aligns closely with the nighttime average in the current study but is still lower than the daytime average.
The significantly elevated noise levels during the day and night in this study may be attributed to a high volume of vehicular traffic, urban congestion, and possibly industrial or construction activities in close proximity to residential areas. Even during late-night hours, when noise levels typically decrease, the recorded levels are still relatively high compared to the prescribed standards by regulatory bodies such as the Central Pollution Control Board (CPCB) in India.
The implications of these findings are concerning, as chronic exposure to elevated noise levels, particularly in residential areas, can lead to various health issues, including sleep disturbances, cardiovascular diseases, and increased stress levels. The comparison with other studies underscores the need for more effective noise control strategies, particularly in densely populated urban areas where noise pollution remains a pervasive issue.
Commercial Areas
The results of this study showed that noise levels in commercial areas vary significantly throughout the day. The mean noise levels reported were 79.67 ± 2.97 dB during the day, 74.86 ± 1.75 dB at night, and 61.33 ± 2.13 dB during the late-night hours (1 AM-6 AM). The maximum recorded noise levels reached 84.96 dB at Kamod Circle during the day, 77.78 dB at Narayanpura Char Rasta during the night, and 64.92 dB at APMC Market - Bus stop in the late-night period, with minimum levels of 75.08 dB (Shivranjani Junction), 72.06 dB (Pushpkunj - Bus stop), and 58.03 dB (Surdhara Circle), respectively. This shows that commercial areas have larger swings in noise levels, presumably due to late-night activities such as restaurants, pubs, or late-night transportation. During the late-night period, the average noise level declined to 61.33 dB, with a range from 58.03 dB to 64.92 dB. The prevalence of late-night noise in business districts, albeit lower than daytime levels, still illustrates the continuous activity that can potentially harm adjoining residential zones (Fig. 4).
When compared to earlier research focused on business areas, the noise levels in this study appear significantly elevated. For instance, a study by Chauhan et al. (2010) revealed average noise levels in commercial areas of Delhi ranging from 68 to 74 dB during peak hours, which is lower than the average daytime levels recorded in the current study. Additionally, Goswami & Swain (2017) recorded commercial area noise levels in Bhubaneswar, Odisha, averaging around 75 dB, which is still below the day and night averages observed here. The greater noise levels during the day in commercial districts can likely be ascribed to heavier traffic, increased economic activity, and the presence of several commercial establishments working simultaneously. The noise levels at night remain relatively high as well, indicating extended business hours and overnight motor activity. Even during the late-night hours, when commercial activity often diminishes, the reported noise levels are still above what is typically deemed appropriate for calm areas.
These elevated noise levels are a matter for concern, since they can contribute to significant health effects, including stress, hearing impairment, and cardiovascular concerns for persons who work or spend extended periods in these commercial zones. The comparison with other studies underscores the necessity for tighter enforcement of noise laws in commercial areas, particularly during peak hours, to defend public health.
Industrial Areas
The data collected from the industrial regions demonstrated that noise levels were notably high across all hours of the day. The mean noise levels measured were 80.62 ± 2.83 dB during the day, 74.29 ± 1.82 dB at night, and 61.47 ± 1.66 dB during the late-night hours (1 AM-6 AM). The greatest noise levels reached 84.75 dB at Sanand Chowki during the day, 77.86 dB at Swastik Industries during night, and 64.67 dB at Sitaram Bapa Chowk in the late-night hours. The minimum noise levels measured were 75.5 dB during the day, 72.12 dB at night, and 58.66 dB during late-night hours. When comparing these findings with previous research conducted in industrial settings, the results are consistent with or somewhat above the noise levels reported in similar contexts. For instance, Khan & Lone (2017) investigated noise levels in industrial regions of Delhi, where they recorded daytime noise levels ranging from 78 dB to 82 dB, which agrees with the current study’s findings. Similarly, another study by Singh & Davar (2004) in Kanpur's industrial zones found daytime noise levels between 76 dB and 81 dB, which are equivalent to the average levels recorded here.
The constant high noise levels in industrial regions can be attributed to the continuous operation of heavy machinery, increased vehicular mobility connected with industrial activities, and other noise-generating procedures such as loading and unloading of products. These operations contribute to persistent high noise levels throughout the day and night, providing considerable health concerns to workers and neighboring communities. Prolonged exposure to such elevated noise levels has been connected with poor health outcomes, including hearing loss, hypertension, cardiovascular disorders, and stress-related conditions.
Comparative Analysis and Implications
The comparison analysis revealed that noise levels are consistently higher in industrial regions, followed by residential and commercial sectors. The decreasing trend in noise levels from day to late night across all zones showed a natural decline in activity. Nonetheless, the continued presence of relatively high noise levels in commercial and industrial districts suggests the necessity of strict noise management measures, especially at night and late at night. For residential areas, there is a clear need for legislation and enforcement to limit noise levels, especially at night, to ensure the health and well-being of residents. To reduce health hazards and adhere to occupational safety regulations, industrial locations must adopt noise control measures and provide workers with appropriate hearing protection.
The comparative examination of noise level studies across several cities in India, as well as in Bangladesh and Qatar, demonstrates a major and widespread issue of noise pollution, particularly in urban contexts. For instance, in Delhi, studies repeatedly reveal that noise levels in commercial, industrial, and residential zones frequently exceed authorized limits, with levels ranging from 66.5 to 84.7 dB(A) in most places (Chauhan, et al., 2023). Similar findings are reported in Moradabad, where noise levels in residential zones ranged between 72.86 to 109.70 dB(A), and in Haridwar, where noise levels reached up to 102.4 dB(A) in specific places (Chauhan, et al., 2010; Sharma, et al., 2016). These high noise levels are mostly related to transportation and industrial operations, which are prominent in densely populated urban regions.
In Qatar, traffic noise at major intersections remained continuously high, with values between 67.6 dB(A) and 77.5 dB(A), even during weekends, showing a chronic concern with noise pollution (Khadija & Khaled, 2022). Similarly, in Chattogram, Bangladesh, noise levels were reported at worrisome heights, sometimes reaching up to 90 dB(A), indicating serious noise pollution issues in urban areas (Masum et al., 2021). The impact of road traffic is particularly evident in Indian cities like New Delhi and Surat, where noise levels near sensitive locations such as schools and hospitals often exceed acceptable limits, creating major health hazards (Ranpise, et al., 2022). For example, in South Delhi, noise levels were reported to be as high as 81.1 dB(A) near main roadways surrounded by high-rise structures (Alam, et al., 2021).
The COVID-19 pandemic provided a new perspective, as shown in Kanpur, where there was a considerable drop in noise levels during lockdowns, revealing the deep influence of human activities on urban noise pollution (Mishra, et al., 2023). Health implications, such as increasing incidences of hearing damage found in Odisha, underline the chronic effects of continuous noise exposure (Sahu, et al., 2020). Additionally, the geographical analysis of noise pollution in Puducherry underscores the need to understand noise pollution patterns to inform urban design and mitigation methods, with 17% of the sites being classified as high noise sources (Devasia, et al., 2022).
Noise Heat Maps
The use of QGIS software for generating noise heat maps provided a comprehensive way for displaying and analyzing spatial fluctuations in noise levels across different times of the day. By utilizing dB values obtained during morning hours, night hours (10 PM-1 AM), and night hours (1 AM-6 AM), the noise data is efficiently transformed into a visual format that enables for easy interpretation and comparison.
The construction of noise contours by the triangulation of noise data, specifically utilizing a Triangular Interpolation Network (TIN), permits the creation of a continuous surface that reflects noise distribution with a high level of accuracy. The introduction of contour lines at 2 dB intervals significantly enhances the precision of these maps, offering unambiguous demarcations of noise intensity levels across the research region (Fig. 5).
The resulting heat maps demonstrate considerable regional and temporal fluctuations in noise levels. For instance, the maximum noise level measured during the morning hours was 84.96 dB at Kamod Circle, while the minimum was 75 dB at Sardar Patel Seva Sankul - Bus Stop Haridarshan Park, Jashoda Nagar. During the late-night hours (10 PM-1 AM), the maximum noise level was measured at Manekbaug Cross Road (77.9 dB), with the lowest at G.C.S. Medical College - Bus Stop (72.03 dB). In the early morning hours (1 AM-6 AM), the noise levels declined considerably, with the maximum being 64.92 dB at APMC Market - Bus Stop and the lowest at Surdhara Circle (58.03 dB).
These findings were consistent with the expected diurnal variation in noise levels, where higher noise levels frequently occur during peak traffic hours in the morning and late evening, and lower levels during the quieter early morning hours. Urban planners and legislators can identify problem regions and create focused noise reduction measures by using heat maps, which provide a visual representation of noise pollution. The spatial representation of noise levels through these maps can also improve public awareness and engagement, as the visual format is more accessible than raw data.
The usage of QGIS in this context highlights the software's adaptability in environmental research, particularly in the analysis and management of urban noise pollution. These heat maps add to our understanding of the spatial dynamics of noise pollution in urban environments by offering a thorough and rigorously scientific representation of noise data.
Correlations
The correlation matrix provided shows the relationships between noise levels during three different time periods: day, night, and nighttime (1 am-6 AM). Here's the interpretation:
The strong negative correlation between day and night noise levels (r=-0.989) suggests a distinct variation in noise patterns between these periods, possibly due to differences in human activities and traffic patterns. Typically, noise levels are higher during the day due to increased activity, and lower at night when most people are resting, except for some potential nighttime industries or events that might increase noise levels. The weak correlations involving the nighttime (1 am -6 AM) and daytime (r = .044) suggest that this time might have a more independent noise pattern, possibly influenced by a different set of activities (e.g., late-night traffic or early morning industrial activities). The very low correlation values indicate that noise levels during early morning hours are not strongly linked to either daytime or nighttime noise patterns.
The provided correlation matrix describes the relationships between noise levels in three different zones: Residential, Commercial, and Industrial. Here's the interpretation:
The extremely high correlations between the noise levels in Residential, Commercial, and Industrial areas suggest that the factors affecting noise pollution are quite uniform across these zones. This could imply that the same noise sources, such as traffic, industrial activities, and general urban noise, are impacting all areas equally. The perfect correlation between Residential and Industrial areas (1.000) might indicate that these zones are geographically close or share common boundaries, where noise from industrial activities could significantly affect residential areas. It may also suggest that there is a lack of sufficient noise regulation or mitigation measures to buffer residential zones from industrial noise. The near-perfect correlation (0.998) between Residential and Commercial areas could imply that commercial activities, which might include retail stores, restaurants, and business operations, contribute significantly to noise pollution in residential neighborhoods. This close relationship might affect the quality of life for residents, particularly during peak commercial hours.
The results indicate a need for targeted noise control policies and urban planning strategies that consider the close interrelation of noise levels across different zones. Effective noise management might include establishing noise barriers, implementing stricter noise regulations in industrial and commercial areas, and designing urban layouts that minimize noise exposure to residential areas. Understanding the high correlation between these zones is crucial for mitigating the potential health impacts of noise pollution on urban populations.