Step 1: Alternate grouping: by setting:
Urban noise sources can be grouped as (a) outdoor — traffic, construction, industry, festivals and (b) indoor — household appliances like TVs, mixers, and air conditioners at high volume.
Step 2: List them this way:
Outdoor sources dominate (traffic, factories, construction, loudspeakers); indoor sources like household gadgets contribute on a smaller scale.
Step 3: Final Answer:
Traffic, industries, construction sites, and loudspeakers/festivities are the chief outdoor sources, with household appliances as a minor indoor source.