Tin, lead and their alloys, due to their low melting temperatures and wide availability, are the most commonly used solder materials. In fact, lead has been used as a soldering metal for water pipes (also made of lead) even in Roman times, hence the scientific name for lead, Plumbum. Mechanical Properties.
hearing impairment - impairment of the sense of hearing. hearing disorder. disability, disablement, handicap, impairment - the condition of being unable to perform as a consequence of physical or mental unfitness; reading disability; hearing impairment. deafness, hearing loss - partial or complete loss of hearing.
The usual definition of a hearing impairment is any lessening of a person's ability to hear. Under the Individuals with Disabilities Education Act (IDEA), hearing impairment has a special meaning. It is a permanent hearing loss or a decrease in hearing that is so significant it negatively affects a child's performance in school or ability to learn.