 So, this is the motor bucket that we designed to generate the primary airflow in a machine. It houses a brushless motor to which this impeller is connected here. So, the impeller is the part which is generating the airflow in the product when it is being spun by the motor. However, when it does so, when it spins, its nine veins generate a very particular high-pitched whistle. So, if we turn it on, we'll hear it. So, we're going to recreate the whistle generated by the impeller. Now, if I put the two bits of the rig together, at the moment, the Hummel's cavity here is obstructed by this bit of paper. It's invisible to the sound, so the sound waves travel from the speakers along the tube and then exit and you can hear it. Now, if I unblock the silencer, the sound is being attenuated. The sound waves are being trapped between the silencer here and the speaker there in this fashion. Naturally, the calm go past the silencer and it won't exit the system. So, on this graph, we're looking at the amplitude of sound in decibels against the frequency of sound in hertz. We can see that on this region, the sound is clearly reduced and it's right at the location of this peak here, which represents the whistle that we're trying to attenuate. However, on the full machine, the silencer doesn't look like this. It looks more like that because we've had to integrate it into the product.