Automatic Volume Control
What AVC Does
An automatic volume control (AVC) automatically adjusts the volume, or loudness, of an audio signal, usually to compensate for ambient noise in an effort to make the audio signal better heard and understood above the noise. An AVC is primarily used to enhance intelligibility of speech or appreciation of music heard by the user in noisy environments. Most conventional AVCs attempt to keep the signal-to-noise ratio (S/N) constant for the user.
Where AVC is Needed
AVC is needed wherever a changing noise background can make it difficult to hear or understand an audio signal:
- In cars, to compensate for road noise, wind, traffic, open windows, fans, radios, and occupants talking
- In public places, such as airports, malls, stadiums, meeting halls, stores, markets, lobbies, to compensate for what is mostly human-generated noise
- Outdoors, to compensate for wind, traffic noise, and passersby
Potential AVC Applications
AVC has potential applications in any audio devices or platforms that are sometimes used in noisy environments:
- Mobile phones, including smartphones
- All other handheld audio devices
- Headsets, such as Bluetooth-enabled earpieces
- Personal media players, such as MP3 players
- Car radios and sound systems
Many users of phones with conventional AVC believe that sound clarity is diminished when the AVC is turned on. In fact, in many phones the default setting for the AVC feature is ‘Off.’ Conventional AVC has not progressed beyond the first generation that focuses on loudness of the noise, rather than intelligibility of the signal.
AMD (Advanced Micro Devices) described the first modern digital AVC in U.S. Patent No. 5,666,426 in 1996. The patent proposed a supplementary microphone on a car radio to measure total ambient noise.
Nokia modified this invention in 1999 with U.S. Patent No. 5,907,823 by measuring not total noise, but rather the A-weighted noise level, which is a measure of how loud noise sounds to the human ear. The invention keeps constant the ratio of signal to A-weighted noise (S/NA).
Conventional AVC can be found today, with default setting ‘Off,’ on many mobile phone models from Nokia, LG, Motorola, Sony, RIM, and others and on Bluetooth headsets from Jabra, Samsung, and others.
AVC tackles a universal problem with mobile phones and other portable communications devices – the user can’t consistently hear and understand clearly. A survey reported at an AARP conference that 57% of baby boomers with mobile phones had trouble using them because of their hearing loss, and 30% of those with hearing loss said the problem is mostly their hearing. Significantly, 40% said they would use their mobile phones more if they could hear better. The benefits of AVC, all of which could lead to an expanded customer base, are:
- Increased customer satisfaction
- Easier hearing
- Improved intelligibility
- Enhanced user experience
Forty percent would use phones more if they could hear better