what materials are used for making a sound proof generator which was normal generator?

Question

normal generator was 90-95dB
SOUND PROOF 60-65dB

Answer 1

Here are a few ideas on reducing generator noise, taken from my generator web site.
http://members.rennlist.org/warren/generator.html

Choose an operating location as far away as possible. Note that a larger gauge wire is needed to reduce voltage drop as line length increases. Reducing line loss is required to minimize power loss and to ensure maximum power is available to the house. Lights will flicker less when heavy loads are attached.

Change the exhaust system. Noise from the portable generator systems comes primarily from two sources, the engine block and the exhaust system. With an air cooled engine there is little you can do about block noise. Some engines can have a larger muffler attached or make other changes to the exhaust system. Merely mounting exhaust pipe vertically will noticeably reduce noise.

Build a noise shielding enclosure. This could be as simple as a piece of plywood to reflect sound away from the house to a separate shed to hold the generator. Design your enclosure with safety in mind. Provide adequate air circulation and ventilation to prevent heat buildup and to remove carbon monoxide.

If the noise bothers your neighbors, invite them over for coffee or offer to run line to their home to power the freezer or a few lights. Talk to them before starting the engine, ask they let you know if the noise is bothersome before they phone the police or harbor any resentment. A little diplomacy can go a long way.

Last resort, shut off the engine or buy a quiet generator.

Answer 2

better mufflers and bolt it down