Abstract: There are four methods to express sound insulation standards: （1） sound insulationquantities, （2） sound insulation or protection margins, （3） fixed reference curves and （4） a single dB value.
The requirements of airborne sound insulation in different countries are nearly the same and comply with the human reaction, hut the standards of impact sound level disperse widely and have no close connection with the hearing. To ensure good living environment, most countries have based their standards on field measurements. The difference of corrections for sound insulation measurements, even in ordinary rooms, may be as high as 3dB, due to different definition of normalization. It is suggested that no normalization is to he taken, not only for convenience but also for better description of the living condition. As to the greatest permissible deviation in any frequency band, specification are different in different coutries and no unified value has been arrived yet.