Hi,

Has anyone in the community done biking experiments with NIRx NSP2 system?

Our lab did a biking experiment where the subjects biked outdoors on a park bike route while fNIRS data were collected on their head at the same time by NSP2. However, high-frequency noise exists in the accelerometer data (5-7 Hz). My hypothesis is that this high-frequency mechanical noise might come from the bike and alias the nirs data resulting in very noisy nirs data. The sampling rate is 10 Hz in nirs data, and the high-frequency noise frequency is above the Nyquist frequency of it. Thus this high freq noise is not picked up by nirs data but might alias it and the nirs data is too noisy to see any heartbeat. 

I have attached screenshots of one example of ACC and NIRS data and their spectrum figures.

We are wondering if anyone else has observed the same phenomenon and how they solve it. Please let us know.

Thanks!

Yuanyuan