Analog versus Digital Hearing Aids
Analog hearing aids have been available for many years. They have a microphone to collect sound and convert the sound into electrical energy, an amplifier to increase the strength of the electrical energy, and a receiver or speaker to convert the electrical energy to an acoustic sound. Analog hearing aids may help amplify soft sounds without over-amplifying loud sounds through a process called automatic gain control (AGC). However, analog hearing aids do not typically have other advanced features.
Digital hearing aids are more complex. With digital hearing aids, a microphone picks up sound, which is then converted into digital signals. The digital signals are then processed by the small computer chip in the hearing aid. Once the digital signal is analyzed and processed using Digital Signal Processing (DSP), it is converted into acoustic sound. DSP allows for changes in volume, but can also provide noise reduction and other features to help improve communication in difficult listening environments.
Currently, very few analog hearing aids are available, and most hearing aids contain DSP. Within digital hearing aids, however, many different features are available and are discussed further in this section.
Gain (volume) Processing
For many years, hearing aids have been able to automatically increase or decrease volume depending on the input sounds. This feature minimizes the need to physically adjust the volume control. However, for most patients with hearing loss, simply increasing or decreasing the volume does not improve the clarity of speech. You may be decreasing sounds that are too loud, but at the same time decreasing sounds that need to be increased to improve speech understanding. You may often notice this with the volume control settings of your television or radio.
More recently, hearing aids are able to separate sound into different frequency (tonal) regions, called channels. The volume of each channel can be adjusted independently, allowing for certain sounds to be amplified more than others, similar to an equalizer on a stereo. The amount of amplification in each channel can generally be adjusted by your audiologist using the hearing aid programming software.
Manual volume controls to change the overall volume are available on many hearing aids. Volume controls may be accessed by a button or volume control wheel on the hearing aid or, in some cases, with remote control.
Number of Frequency Channels
The number of channels available for programming differs among hearing aids. With more channels, hearing aids can be programmed to more accurately fit your hearing loss. Also, with more channels, the analysis of the sound environment is more accurate, which can enhance the function of other hearing aid features. However, more is not always better. More than 15 to 20 channels can cause sounds to become ‘muddy