# Branca testing equipments for acoustic materials

## Branca Idealair produces testing equipments to measure the acoustic impedance and NLF of acoustic materials

Our testing equipments get successful results also in the several studies and solutions for the Precision acoustics, the acoustic impedance and the Non-linear factor of materials (**NLF**).

### BRANCA RAYLS 37X - ACOUSTIC IMPEDANCE and NON LINEAR FACTOR

**DETERMINATION OF Specific airflow resistance or “Acoustic impedance”**expressed in MKS Rayls or CGS Ohms (referred to 1 cm2), representing the result of pressure difference across the sample divided by the linear velocity of the airflow; MKS Rayls test procedure states to calculate the ratio between pressure drop (Pascals) and air velocity (meters per second) crossing the sample material. The airflow must be sufficiently low to obtain laminar, non turbulent airflow through the sample, in order to properly define the airflow resistance in a linear range.

**DETERMINATION OF NON-LINEAR FACTOR (LINEAR and TURBOLENT AIR FLOW)**

Non-Linear factor, which allows to check the behavior of the sample at a very high air velocity (turbulent air flow); The second test method is the measure of the NLF - Non Linear Factor.

Examples of applications requiring

When turbulence happens, the measured airflow resistance is higher than in the linear range. This might lead to an undesired change of the acoustic performance of the final component .

It is possible to measure this deviation by calculating the ratio between two measured values of specific airflow resistance, respectively at laminar and turbulent airflow (usually, at 0,2 m/s and 2 m/s airspeed).__NLF measurements__:- Acoustic devices - performance across narrow slots;
- Acoustic devices - nonlinear performance at very high SPL;
- Sound suppression panels working at high SPL;