The Record - Issue 20: Spring 2021

67 sounds, the result is a blurring of the signal. If you are on the receiving end when this blurring happens, it will sound as if the speaker were standing in a bathroom. To ensure a high-quality audio experience, speakerphones need to be sensitive to the direc- tion of speech, as opposed to the direction of the sources of noise and reverberation. This is known as a directional microphone system. These microphones are all designed with a cer- tain ‘pick-up pattern’ which determines how sensitive it is to sound arriving from any specific direction. The most common pick-up pattern is omnidirectional. To produce a directional pick-up of sound from a series of omnidirec- tional microphones, you need to take advan- tage of differences in both the level of sound and the time at which it arrives at the different microphones. This type of directional micro- phone system is known as a microphone array beamformer. The delays in sound arrival make it possible to align the signals so that they are synchronised, and the subsequent summation of these signals increases the output level of the microphone array for a certain direction, while decreasing the output level for others. An omnidirectional microphone will pick up both target speech and unwanted surrounding noise sources equally, but not when advanced beamforming is used. In this instance, speech arriving from the direction that the beam is pointing will be picked up without any change while sounds arriving from other angles will be greatly reduced. As discussed, reverberation causes sounds to arrive at a speakerphone with additional delay and from additional angles. This results in a blur- ring of the signal in time, reducing the intelligi- bility of speech. An enhanced ratio of speech to reverberated sound is maintained throughout the use of a beam focused on the direction of the tar- get signal. Sounds arriving at an angle, reflected from the room’s surfaces will be lessened. With the help of microphone array beam- forming, speakerphone systems such as EPOS’ EXPAND 80 Series, are equipped with a focused, steerable beam that can optimise individual voices in the meeting room for remote listeners. This level of advanced technology empowers remote teams to collaborate with the same levels of confidence and clarity as if being there in per- son – something that cannot be taken for granted as we head into a future of hybrid work. Jesper Kock is the vice president of research and development at EPOS