In order for a speakerphone to not clip the conversation, it must be a true full-duplex system, meaning that audio must flow continuously from each end to the other. Conventional speakerphones do not do this, they operate by switching audio back and forth, and so cause clipping. Only speakerphones certified by the manufacturer as being true IEEE 1329 Class 1 full-duplex systems will give good non-clipping performance. Moreover, the instruments at both ends, not just one end, must be full-duplex systems, whether handset telephones or speakerphones. Note that the “speakerphone” function built into most handset phones does not meet this performance standard; even most systems labeled as “full duplex” are in fact half-duplex speakerphones most of the time unless the manufacturer clearly specifies their compliance with IEEE 1329 Class 1 specifications.
The endpoint environment can also be a source of clipping; background noise in particular should be kept to a minimum. High levels of noise can confuse both full-duplex and half-duplex speakerphones, and cause them to switch the voice in and out unpredictably. Fan noise, air conditioner noise, overhead projectors, outside construction or traffic, or background conversations can contribute to this problem. If this is suspected, try moving to a quieter environment and see whether the problem goes away.
Another endpoint environment that can cause problems is one that has peculiar reverberation properties. Rooms with many reflective surfaces, such as large windows and whiteboards, can have unusually high reverberation. This will make a person who is three feet from a speakerphone sound like they’re fifteen feet away, and can also cause a full-duplex speakerphone to make occasional errors in its efforts to avoid clipping. So this situation is best avoided for a number of reasons when possible.