stationary

Returning to the weekly meeting place, there are two kinds of noise. Still sound and nonsteady sound (or dynamic sound). Static noise arises from constant clicks generated by light fixtures. This type of noise can be easily detected and eliminated using traditional signal processing techniques such as Wiener or Kalman filter. These techniques rely on noise with some degree of statistical regularity and are the standard part of many commercial audio pipelines. Removing dynamic noise is more difficult. Hyena noise is a good example of nonstationary noise. The following figure shows the hyaena audio waveform, the spectrogram and the statistical regularity (white noise) of the HVAC system noise.

There are many sources of noise pollution in urban areas. Normally, the source is fixed or mobile. Examples of fixed sound sources include festivals, elections, temples worship, mosques, advertisements, use of bulldozers, drilling and explosives to break rocks, household equipment such as vacuum cleaners, televisions, radios, stereos, grinders, There are speakers used in various situations. Mixers On the other hand, mobile sources can be categorized as traffic / traffic noise (road traffic or road noise), industrial noise, construction noise and adjacent noises.

Fixed energy, waste and border road transport are most likely to reduce greenhouse gas emissions. Kerosene and biomass fuel are the main sources of greenhouse gas emissions from housing. Of 71 Mt Co 2 e emissions from fixed energy sources, nearly 75% are from kerosene combustion, 12% are from wood and charcoal. Addis Ababa's greenhouse gas emissions are low is mainly due to zero emissions supply and lower electricity charges. Currently, only about 17% of the population of Ethiopia lives in the city, and Addis Ababa has nearly 5% of the population. CRGE forecasts that the population of urban areas will increase by 4% per year, and by 2030 will exceed 30 million people. The number of cities that increase at an unprecedented rate has increased, and the emissions of greenhouse gases are increasing at an alarming rate