Normal to abnormal behavior of PbSiO3 glass: A vibrational spectroscopy investigation under high-pressure

•Brillouin investigation of PbSiO3 glass cold densified at different maximum pressure.•Densification induces anomaly in elastic modulus despite the low silica content.•The verified anomaly distinguishes from the elastic anomaly then absent in this glass.•Abnormal decrease on longitudinal sound velocity whereas the density increases marginally.