Audio Devices for Videoconference Use
With any video-conference (v/c) client software, audio plays an extremely important role- more important, in fact, than that of video.
It is quite possible to hold a successful v/c conversation during which the quality of the video is less-than-ideal; the reverse, however, is not the case. Quite simply, the audio quality must be of a high standard. For voice, this does not require hi-fi quality transmission and reception from 20Hz to 20kHz or more. Rather, there are some fundamental principles that need to be addressed.
- There must be no feedback path between audio-in (a microphone) and audio-out (usually a loudspeaker). If there is, it will result in an echo being introduced into the audio, resulting in an annoying artefact at best, to complete unintelligibility at worst. This separation may be achieved by, for example
- use of a headset, with integral microphone and headhones (suitable for individual users only)
- use of echo-cancelling hardware/software which allows a microphone for room audio pick-up from attendees at the same time as they are listening to the audio from remote sites via loudspeakers
- Ambient noise in the room should not be transmitted to other sites
- The acoustics of the room should not adversely affect the quality of the transmitted audio (or of the received audio as heard by the local audience)
- The essential frequency range of human speech should be covered by both the audio-in and audio-out hardware; this may mean only up to about 8kHz or so, or even less. Most of the power in the human voice is found up to around 4kHz, with higher frequencies providing extra definition and intelligibility.
In essence, the audio hardware and set-up used should be, in a sense, "invisible" to the user- conversing during a v/c session, whether one-to-one or in a group, should be as comfortable as talking face-to-face in person.
Suitable hardware
1. Headset The simplest solution, but suitable only for individual use. Depending on the price and quality, these are capable of producing very clear audio, with essentially no feedback, and can be comfortable to wear for extended periods. Some of these are USB devices, whilst some are analogue with separate in/out jacks, which will not be directly compatible with some Macs.
Pros : simple, cheap; no echo.
Cons : single-user only; may be uncomfortable for longer sessions
2. Integrated echo-cancelling microphone/speaker unit These self-contained units incorporate both one or more microphones for speech pick-up, and a speaker for output. They allow the user to converse in a very natural way, and allow more than one local person to participate in the conversation. There are a number of such devices about; good examples include the Clear One Chat 50 and the Clear One Chat 150 USB (pictured). These devices include echo-cancelling routines which mean that they take care of that problem automatically. Depending on the device, they are suitable from a single user to around a dozen or so.
Pros : can have very good sound quality; very simple to use (almost plug-and-play); comfortable to use; can accomodate several participants; reasonable price
Cons : single units not suitable for larger venues; internal microphone is the only audio input (very rarely would this be a problem, though)
3. Echo-cancelling microphone In this case, the microphone and speaker systems are separate, but the microphone itself has built-in echo-cancelling capability. Thus the microphone is used as the audio input to the host computer, and an external amp/speaker system is connected to the host computer's audio output. An example is the Clear One AccuMic (pictured). From experience, it is found that this particular device benefits greatly from use of an external hardware audio mixer prior to the host-computer's sound card, in order to provide finer control over gain settings. For usage up to about 12 people, the Chat 150 may prove a simpler and more convenient solution, and may be preferred if a self-contained combined microphone/speaker unit is an option.
Pros : relatively easy to use (with some caveats); suitable for groups up to about 12; independent of sound reproduction system
Cons : sensitive to relative placement in room cf. speakers; single units not suitable for larger venues; internal microphone is the only audio input (very rarely would this be a problem, though)
4. Combined hardware/software multi-input system These devices allow multiple audio input sources whether microphones or other sources, have sophisticated audio-control software with in-built hardware signal-processing, and connection to larger room sound reproduction systems. This provides the greatest flexibility in terms of audio inputs (and thus of possible uses and extension of v/c technology), greatest refinement of echo-cancellation and noise-reduction capabilities, and versatility of distributed sound reproduction in the room.
Thus, multiple microphones may be placed for distributed room pick-up, allowing larger venues to be catered for. Also, the ability to patch-in other audio sources allows "non-traditional" use of v/c systems, such as distributed, collaborative musical performance. Of course, this all comes at a much higher price, increased hardware complexity, and greater necessity for adjusting and tweaking of settings for best results. For larger venues, and for the best possible results, such systems are required.
A good example is the Clear One Converge Pro 880 (pictured).
Pros : great versatility in combining audio sources; refined echo-cancelling and noise-reduction routines and settings- best overall sound quality; much larger venues and audience numbers may be accomodated whilst maintaining two-way audio
Cons : expensive; greater set-up and operational complexity
In the above discussion of hardware, the specific items directly referred to are ones for which various users' experiences and opinions are known. Their listing here is in no way to be interpreted as a suggestion that these are the only such units which can be used; rather, that these ones are in use, and their characteristics are known.