DA DB-HR / 2 - Indirect Transmission Calculation Procedure
The DA DB-HR / 2 is a technical support document issued by the Ministerio de Fomento through the Secretaría de Estado de Infraestructuras, Transporte y Vivienda in Spain. Updated in March 2020, this document functions as a technical guide to assist in the comprehension and implementation of the Código Técnico de la Edificación (CTE), specifically the Documento Básico DB-HR Protección frente al ruido. While it lacks regulatory status itself, it provides the calculation procedures approved by the Ministry's technical services to comply with the mandatory requirements of the DB-HR general option.
The scope of this document covers the estimation of acoustic performance in buildings based on the performance of individual elements. It focuses on indirect or flanking transmissions for both airborne noise and impact noise in scenarios not explicitly detailed in section 3.1.3 of the DB-HR. The methodology is based on the simplified model for global values defined in UNE-EN ISO 12354 (parts 1, 2, and 3) and can also be applied to detailed frequency models. It defines parameters such as the vibration reduction index (Kij) and the direction-averaged vibration level difference (Dv,ij,n).
This document categorizes construction elements into Type A (homogeneous elements like reinforced concrete or CLT) and Type B (framed elements such as plasterboard on metal studs). It provides specific algebraic expressions for various junction types, including rigid T-junctions, cross junctions, and joints incorporating elastic bands.
Classification of Construction Elements
The calculation procedure distinguishes between two fundamental types of construction elements based on how vibration energy is transmitted through junctions.
- Type A elements: Homogeneous elements such as reinforced concrete, cross-laminated timber (CLT), brickwork, or concrete blocks. These elements are characterized by a specific structural reverberation time and a vibration level decrease of less than 6 dB perpendicular to the joint line.
- Type B elements: Framed construction elements consisting of laminated gypsum boards or wood panels anchored to metallic or timber frames.
- Type A/B combinations: Junctions between a homogeneous element and a framed element are typically characterized using the vibration reduction index, Kij.
Calculation of Vibration Reduction Index (Kij)
The Kij index is used for Type A elements and combinations of Type A and B. Its value depends on the magnitude M, defined as the ratio of surface masses of the elements forming the junction.
- Magnitude M: Calculated as the logarithm of the ratio between the mass per unit area of element i and the mass per unit area of the perpendicular element j.
- Frequency range: The global value of Kij is determined as the arithmetic mean of the values in the one-third octave bands from 200 Hz to 1250 Hz.
- Surface mass exclusion: When calculating M, only the base element or floor slab mass is considered; layers such as floating floors, linings, or suspended ceilings are excluded.
Specific Junction Types and Formulas
The document provides specific formulas for different structural configurations of homogeneous elements to determine the transmission of vibrations.
- Rigid cross junctions (+): Characterized by equations 3.2 and 3.3 for internal transmission paths.
- Rigid T-junctions: Governed by equations 3.4 and 3.5.
- Junctions with elastic bands: For transmissions crossing one or two elastic joints, the document applies a correction factor, Δ1, which depends on the load over the joint and the reference load of 100 kN/m².
- CLT junctions: Specific formulas (3.18 to 3.22) apply to cross-laminated timber joints with mass ratios between 0.5 and 2.
Direction-Averaged Vibration Level Difference (Dv,ij,n)
For Type B elements, indirect transmissions are characterized by the parameter Dv,ij,n. This value is essential for calculating the flanking sound reduction index Rij and the flanking impact sound pressure level Lnij.
- Inner leaf contact: Calculations for framed elements may consider the complete system or only the inner leaf in contact with the source or receiving rooms.
- Floor-facade T-junctions: For any trajectory between floor and facade, the document specifies a base value of 30 dB plus a frequency-dependent correction (3 dB/octave).
- Double-structure separation walls: Specific values are provided for cross junctions between floors and double-leaf separation walls, ranging from 18 dB to 38 dB depending on the transmission path.
Frequently Asked Questions
What is the difference between Type A and Type B elements in DB-HR?
Type A refers to homogeneous elements like concrete or brick, while Type B refers to framed elements like plasterboard on metal studs.
How is the magnitude M defined for vibration calculations?
Magnitude M is the logarithm of the ratio of the surface mass of the element in the transmission path to the surface mass of the perpendicular element forming the junction.
Which frequency range is used to calculate the global Kij value?
The arithmetic mean is taken from the one-third octave bands between 200 Hz and 1250 Hz.
What standard provides the simplified model for these calculations?
The procedure is based on the simplified model for global values found in UNE-EN ISO 12354 parts 1, 2, and 3.
Are floating floors included in the mass calculation for Kij?
No, surface masses of finishing layers like floating floors or suspended ceilings are excluded from the calculation of magnitude M.
What is the reference length for junction calculations?
The reference junction length, denoted as l0, is established as 1 meter.
How are CLT junctions handled in this document?
Specific formulas are provided for CLT (cross-laminated timber) junctions where the mass ratio per unit area is between 0.5 and 2.
What is Dv,ij,n used for?
It represents the direction-averaged vibration level difference, used to characterize the transmission of acoustic energy through junctions between Type B framed elements.
