Regarding this method (however, estimated values are reference values and not guaranteed values)

• This is a method to easily estimate air noise sound insulation performance (room-to-room average sound pressure level difference: D value) between two rooms at the work site by people other than acoustic experts. D value is devised to be obtained by subtracting the reduction value of the sound insulation performance by the construction situation of the site and the design specification of the actual room from the air sound insulation performance (TLD value) in the laboratory of the sound insulation wall. It is provided in a checklist form.
• This method is based on the actual measurement example of our company with reference to recommended values of "Design Material for Sound Insulation in Buildings” and "Performance Standard and Design Guidelines for Sound Insulation in Buildings” edited by the Architectural Institute of Japan, as well as other various documents .
• The reason why the estimated sound insulation performance at the site has the minimum to maximum range is that there are large differences in the sound insulation performance of parts such as windows and doors on site depending on the products, to make it easily estimated by people other than acoustic experts, as well as to keep it limited to general matters by excluding technical matters from the checklist. In addition, in special cases there are many cases where the sound insulation performance decreases beyond the maximum value. Please consider it only as a reference value.
• Walls that can be estimated with this method are walls constructed by the regular construction procedure, walls that are completely sealed in all four sides. This method cannot be applied to walls other than the aforementioned.
  
• Although a check example at the work site is shown in the attached sheet, even if designed to be close to a perfect sound insulation, it will be reduced by about 4 dB. If routed sound is large, it will be reduced by 10 to 15 dB. Therefore, for example, if we install sound insulation wall conforming to TLD 55, it should be D50 if it’s good and D40 to 45 if it’s bad.

Estimation procedure (Estimation should be done by those who understand the drawing and the construction situation of the site)

• The estimation procedure is as follows:
  (1) Carefully read and understand the contents of each item of the checklist, as well as the attached manual.
  (2) Check each item of special reduction factors in the checklist by checking the drawing and the work site carefully.
  (3) Calculate the total of the minimum and maximum reduction factors of sound insulation performance by the following formula:
  (Sum of reduction values) = (reduction reference value) + (total of checked special reduction values)
• Special reduction factor is a factor that reduces the sound insulation performance depending on the situation at the site, and applicable to the sum of checked items in the above equation.
• Reduction reference factor is mandatory and should always be checked. The sound insulation performance of the sound insulation wall itself in the laboratory is reduced because of the presence of sound routing from the floor slab other than the sound insulation wall at the site and the above special reduction factors which cannot be checked. Correction for reduction reference factor is set at -4dB.
• Please refer to the attached sheet "Explanation Diagram of Difference Between TLD value and D value" on the difference in sound insulation performance between laboratory and on-site.
  (4) Calculate the maximum and minimum of estimated D value at the site from the TLD using the following formula:
  Minimum D valueLTLD value - Maximum value of total reduction value obtained in (3)
  Maximum D value = TLD value - Minimum value of total reduction value obtained in (3)
  (D value: estimated sound insulation performance in the actual room)

• Example of how to fill the checklist for estimation method of sound insulation performance (D value) in actual room（14KB）
• Checklist for estimation method of sound insulation performance (D value) in actual room（14KB）