3.2. Comparison of the Average Noise Levels in Ibadan and Ile-Ife
The overall mean noise level for all the locations on all the days of the week recorded in Ibadan was 73.2 dB(A) compared to 69.2 dB(A) for Ile-Ife.
Figure 7 shows that the mean morning, afternoon, and evening noise levels in Ibadan were 74.3 dB(A), 72.3 dB(A), and 73.1 dB(A), which were higher than the average noise levels in Ile-Ife during the same period (68.6 dB(A), 68.8 dB(A), and 70.3 dB(A)) respectively. Additionally, the lowest recorded noise for Ibadan is 58 dB(A), while that of Ile-Ife is 53 dB(A). This signifies that, based on the measurements, the noise pollution in Ibadan is greater than that in Ile-Ife. Noticeable were the mean daily noise levels, which were higher in Ibadan than those obtained in Ile-Ife on all days except for Sunday (
Figure 8).
Figure 7.
Average daily noise levels in Ibadan and Ile-Ife.
Figure 7.
Average daily noise levels in Ibadan and Ile-Ife.
Figure 8.
Mean daily noise levels in Ibadan and Ife-Ife.
Figure 8.
Mean daily noise levels in Ibadan and Ife-Ife.
The noise level readings of both Ibadan and Ile-Ife were also analyzed. The summary of the measurements reveals that 23.5% of the total noise level recorded for the two cities falls within the highly risky zone (65–69 dB(A)), accounting for 141 of the 600 average noise levels recorded. A total of 20.67% of the average noise level falls within the dangerous zone (70–74 dB(A)), 19.67% within the highly dangerous zone (75–79 dB(A)), 16.67% within medium risk (60–64 dB(A)), 10.33 within highly dangerous (80–84 dB(A)), and 5.17% and 3.33% within extremely dangerous (80–85 dB(A)) and risky (55–59 dB(A)) zones, respectively. A smaller proportion (0.67%) of all sampled locations in both Ibadan and Ile-Ife falls within the safe zone of less than 55 dB(A). These readings translate to 79.3% of sampled locations in Ibadan and Ile-Ife experiencing noise pollution that is above the recommended noise level (
Table 5).
Table 5.
Percentile distribution of the recorded average noise levels.
Table 5.
Percentile distribution of the recorded average noise levels.
Noise Level Db(A) | Mon. | Wed. | Fri. | Sat. | Sun. | Total | Percentage | Sensitivity |
---|
55–<60 | 2 | 5 | 3 | 5 | 9 | 24 | 4.00 | Risky |
60–<65 | 13 | 12 | 14 | 15 | 46 | 100 | 16.67 | Moderately Risky |
65–<70 | 23 | 37 | 21 | 30 | 30 | 141 | 23.50 | Highly Risky |
70–<75 | 30 | 23 | 29 | 23 | 19 | 124 | 20.67 | Dangerous |
75–<80 | 28 | 23 | 28 | 29 | 10 | 118 | 19.67 | Highly dangerous |
>80 | 24 | 20 | 25 | 18 | 6 | 93 | 15.50 | Extremely dangerous |
3.3. Relationship between Land Use and Noise Levels
The variation in noise level under different dominant land uses for the three periods of the days of the week were analyzed for each city. Land-use-based distributions of noise in the mornings in Ibadan reveal that residential areas had the least average noise levels of 65.1 dB(A), 66.7 dB(A), and 67.6 dB(A), for mornings, afternoons, and evening, respectively (
Figure 9). This range of values falls within the highly risky zones (65–70 dB(A)), which is more than 10 dB(A) above the WHO-recommended daytime residential noise level of 55 dB(A). The average morning, afternoon, and evening noise levels for transportation land use are 73 dB(A), 69.9 dB(A), and 71.15 dB(A), respectively, falling within the highly dangerous zone (75–80 dB(A)). The recorded commercial noise levels for morning, afternoon, and evening, 76.77 dB(A), 73.97 dB(A), and 75.94 dB(A), are falling mostly within the highly dangerous zone (75–80 dB(A)), more than 20 dB(A) higher than the WHO permissible limit of 55 dB(A) (day/night). The industrial areas recorded 73.7 dB(A) and 73.8 dB(A), which were above the WHO recommended noise level at 65 dB(A) (day/night). All the noise levels in the different land-use types exceed the respective recommended average noise levels.
The average noise levels across different land uses in Ile-Ife are shown in
Figure 10. Results reveals that commercial land use account for 76.77 dB(A), 73.97 dB(A), and 75.94 dB(A) for morning, afternoon, and evening, respectively. These readings fall between the dangerous zone of noise sensitivity (70–75 dB(A) in the afternoons and highly dangerous in the mornings and evenings. These readings exceed the WHO allowable noise limit of 55 dB(A) (morning and night) and US EPA 60 dB(A)/morning and 50 dB(A)/night). The average noise levels for transportation land use in Ile-Ife for morning, afternoon, and evening were 78.92 dB(A), 77.08 dB(A), and 76.8 dB(A), respectively. These values fall in the extremely dangerous zone. Similarly, the residential land use noise levels returned 66.08 dB(A), 65.36 dB(A), and 66.6 dB(A) for morning, afternoon, and evening, falling in the highly risky zone (65–70 dB(A)) and exceeding the WHO standard of 55 dB(A) (morning) and 46 dB(A) (night). The study by [
82] shows similar trend. An interesting range of 70.4 dB(A), 68.6 dB(A), and 70.4 dB(A) was recorded for educational land use in Ile-Ife. This falls in the high risk zone (65–70 dB(A)) and more than 20 dB(A) above the recommended WHO standard of 46 dB(A) for day and 36 dB(A) (night) for silent zone. Land use types in Ibadan and Ile-Ife were compared to the WHO standards for day (morning, afternoon) and night (evening). As shown in
Figure 11, all land-use types considered, in both Ibadan and Ile-Ife, exceed the WHO noise standards.
Figure 9.
Average noise levels and land use in Ibadan.
Figure 9.
Average noise levels and land use in Ibadan.
Figure 10.
Average noise levels and land use in Ile-Ife.
Figure 10.
Average noise levels and land use in Ile-Ife.
Figure 11.
Comparative mean of daily noise levels across land uses in Ibadan and Ife-Ife.
Figure 11.
Comparative mean of daily noise levels across land uses in Ibadan and Ife-Ife.
To evaluate the effect of land use types on noise, a one-way analysis of variance (ANOVA) was conducted with the fixed factor being land use, with four categories; residential, educational, transportation, and commercial, while noise was the dependent variable. The assumption of homogeneity of variance was first tested and the result were found tenable using Levene’s Test, F(3,34) = 1.50,
p = 0.245. The results of the ANOVA test, shown in
Table 6 reveal a statistically significant relationship F(3,34) = 15.13,
p = 0.000. Additionally, the Tukey’s HSD (
Table 7) pair-wise follow-up test revealed that noise levels between residential and transportation land use types (M =−25.32, SD = 4.80) are statistically significant, as with noise levels between residential and commercial land-use types (M = −26.33, SD = 4.52). However, the differences in noise levels between other groups are not statistically significantly.
Table 6.
Analysis of variance of noise levels across land use.
Table 6.
Analysis of variance of noise levels across land use.
ANOVA |
---|
| Sum of Squares | Df | Mean Square | F | Sig. |
Between Groups | 5874.801 | 3 | 1958.267 | 15.132 | .000 |
Within Groups | 4400.151 | 34 | 129.416 | | |
Total | 10274.953 | 37 | | | |
Table 7.
Tukey’s HBD Multiple comparison between noise levels across land use types Dependent Variable: Noise, Tukey HSD.
Table 7.
Tukey’s HBD Multiple comparison between noise levels across land use types Dependent Variable: Noise, Tukey HSD.
(I) Land Use (J) Land Use | Mean Difference | Std. Error |
---|
(I–J) |
---|
Residential | Educational | –7.92000 | 7.19489 |
Transportation | –25.32000 * | 4.79660 |
Commercial | –26.33212 * | 4.51585 |
Educational | Residential | 7.92000 | 7.19489 |
Transportation | –17.40000 | 7.58408 |
Commercial | –18.41212 | 7.40971 |
Transportation | Residential | 25.32000 * | 4.79660 |
Educational | 17.40000 | 7.58408 |
Commercial | –1.01212 | 5.11319 |
Commercial | Residential | 26.33212 * | 4.51585 |
Educational | 18.41212 | 7.40971 |
Transportation | 1.01212 | 5.11319 |
Excessive noise is a major environmental complaint in urban areas emanating from different land uses. Noise disturbance significantly impacts many areas with a high population density and affects the inhabitants in their daily life, sleep, work, and study. The results in the preceding sections detail the compilation and statistical calculations of noise levels in Ibadan and Ile-Ife, as well as the comparative breakdown of noise across both cities. The emergence of Monday and Friday as the noisiest days of the week, in both Ibadan (
Figure 3) and Ile-Ife (
Figure 4), could be attributed to the socio-economic practices of the inhabitant of the cities. The increasing noise generated by the various urban land uses, especially those relating to transportation and commercial activities in Nigeria cities, and by extension in developing countries, is a cause for concern. The average noise level in the residential, commercial, and transportation areas of Ibadan were 65.2 dB(A), 75.9 dB(A), and 75.9 dB(A) (
Figure 9), respectively, while those of Ife were 65.5 dB(A) and 73.6 dB(A) (
Figure 10), which exceed the allowable WHO noise level limits. These computed noise levels,
vis-à-vis explained violations observed in the cities of Ibadan and Ile-Ife, are similar to those reported in other studies [
83,
84,
85,
86,
87].
Noise levels can be influenced by time of day and day of the week. For instance, Monday marks the beginning of many economic activities, and a high inflow of people who left the city for the weekend, while Friday is mainly characterized by the increase of vehicular traffic and mass movement out of the cities by travellers. Hence, results revealed that Mondays and Fridays recorded the highest morning and evening noise in Ibadan and Ile-Ife. The emergence of Sunday as the quietest day of the week in both cities can be explained by the socio-cultural activities of the people in the cities. Traditionally, Sundays are usually devoid of many socio-economic functions, except for religious activities, which in most cases are solemn and take about three to four hours for many places of worship in Ibadan and Ile-Ife. In the light of this, vehicular traffic and movements are always limited, as people often remain indoors to rest from all socio-economic engagements of the previous week and to prepare for the incoming week.
The overall results on noise pollution in different zones of Ibadan and Ile-Ife cities indicates that the noise pressure levels were highly variable and were the manifestation of diverse man-made activities in these zones. However, all readings in this respect are higher than the recommended values and suggest that many of the dominant activities on these land uses are carried out with no respect for the environment. This further shows possible link between the socio-cultural orientation of the people and their use of the environment. Additionally, the mean noise levels calculated for both Ibadan and Ile-Ife was 71.3 dB(A) and this exhibits similar characteristics with results obtained by [
72].
The test of the relationship between noise and land-use types shows that noise in typical urban cities in Nigeria is greatly influenced by prevailing land-use types, and that there is a marked difference in noise levels across different land-use types. The implication for the present noise regime in Nigerian urban areas, as typified by those obtained in the in this study, transcends the health consequences of this environmentally-degrading phenomenon. If not properly checked, the noise levels have the potential to affect the re-distribution of people and socio-economic activities within the centers in such a skewed way that they will influence the spread and economic rent of the centers. The increasing rate of development of sprawls and illegal settlements outskirt of many of Nigeria’s urban centers attest to this fact.