IR labels can be used to study local environments in proteins in a site-selective manner. Neutron scattering experiments complement Raman and IR spectroscopy by delivering information about delocalized vibrational modes that might be vital for enzyme activity. Combining these experimental methods opens up new possibilities to better understand how proteins work. We want to investigate for the first time how IR labelling influences global protein dynamics of T4 lysozyme by using neutron scattering spectroscopy. The IR label itself has a distinct vibrational mode around 2160 cm^-1 that is sensitive towards the local microenvironment around the label. Density of state calculations based on molecular dynamics simulations predict changes in the 2-10 THz region upon labelling indicating changes in global dynamics. The TOSCA spectrometer allows us to observe both energy ranges at the same time.