Ultra-broadband terahertz communication systems are expected to help satisfy the ever-growing need for unoccupied bandwidth. Due to high attenuation of terahertz wave, it can be widely used in indoor WLAN data communication. Future THz WLANs will rely on not only the line-of-sight (LOS) but also the nonline-of-sight (NLOS) channels to perform data communication. Hence, both kinds of channels have to be characterized. In this paper, we present the measures of ultra-broadband channel at 340 GHz for an indoor scenario. The measured channel transfer function is compared with a ray tracing simulation performed with the indoor scenario. Additionally, we show the reflection losses of some building and plastic materials which could be required as input data for the ray tracing algorithm.