The laboratory method (ISO 10140-2:2021) is probably the most accurate method to determine the sound reduction index R of walls. Flanking noise (ISO 10848-1 and 4:2017) is almost fully eliminated in the laboratory setup whereas this is not the case for in situ measurements (ISO 10052:2021). The measurements are even more difficult for measurements in open air or in factory halls with mock-up setups. Manufactures of building elements, such as prefabricated walls, are interested in quick measurements of the sound reduction index R of their products. This paper compares the traditional laboratory measurements, the intensity method and the Sopranoise road barrier method (EN 1793-6) with the vibration velocity / sound pressure method (ISO 140-4:1998). Different setups were measured using different methods in laboratory and in open air. Most of the experiments were done with loudspeakers used as an excitation source, but some were also done with shakers and a tapping machine. The importance of the use of sound shielded accelerometers will be elucidated.