According to the Noise Pollution (Regulation and Control) Rules, 2000, of the Ministry of Environment Forests, India, the day time and night time noise level limits in ambient air for a residential area are 55 dB (A) Leq during the day and 45 dB (A) Leq during the night. Let's explore the reasons behind these limits in detail.

**1. Noise Pollution (Regulation and Control) Rules, 2000**
In India, the Ministry of Environment Forests has established the Noise Pollution (Regulation and Control) Rules, 2000 to regulate and control noise pollution. These rules set noise level limits for different areas and time periods to ensure a peaceful environment and protect public health.

**2. Residential Area Noise Level Limits**
The noise level limits for a residential area are specified in the Noise Pollution (Regulation and Control) Rules, 2000. During the day, the permissible noise level limit is 55 dB (A) Leq, and during the night, it is 45 dB (A) Leq. These limits are set to maintain a comfortable living environment for residents and prevent disturbances during rest hours.

**3. Daytime Noise Level Limit**
During the day, when people are engaged in various activities, a higher noise level limit of 55 dB (A) Leq is acceptable. This limit allows for normal activities and ensures that the noise does not exceed a level that can cause annoyance or discomfort to residents. It also considers the fact that there may be higher noise sources during the day, such as traffic and construction activities.

**4. Nighttime Noise Level Limit**
During the night, when people are resting and trying to sleep, a lower noise level limit of 45 dB (A) Leq is enforced. This lower limit is necessary to provide a peaceful and quiet environment for residents during their rest hours. Excessive noise during the night can disrupt sleep patterns, affect health, and lead to various sleep-related disorders.

**5. dB (A) Leq Measurement**
The noise levels are measured in dB (A) Leq, which is the equivalent continuous sound level. It represents the average sound energy over a specific time period and takes into account the varying intensities of sounds. This measurement is more appropriate for assessing noise pollution as it considers the human ear's sensitivity to different frequencies.

In conclusion, the Noise Pollution (Regulation and Control) Rules, 2000, set the day and night noise level limits in ambient air for a residential area in India as 55 dB (A) Leq during the day and 45 dB (A) Leq during the night. These limits aim to maintain a peaceful living environment, prevent disturbances during rest hours, and protect public health.