Reverberation, in psychoacoustics and acoustics, is a persistence of sound after the sound is produced. A reverberation, or reverb, is created when a sound or signal is reflected causing numerous reflections to build up and decay as the sound is absorbed by the surfaces of objects in the space – which could include furniture and air; this is most noticeable when the sound source stops but the reflections continue, their amplitude decreasing, until zero is reached. Reverberation is frequency dependent: the length of the decay, or reverberation time, receives special consideration in the architectural design of spaces which need to have specific reverberation times to achieve optimum performance for their intended activity. In comparison to a distinct echo, detectable at a minimum of 50 to 100 ms after the previous sound, reverberation is the occurrence of reflections that arrive in a sequence of less than 50 ms; as time passes, the amplitude of the reflections reduces to non-noticeable levels.

Reverberation is not limited to indoor spaces as it exists in forests and other outdoor environments where reflection exists. Reverberation occurs when a person sings, talks, or plays an instrument acoustically in a hall or performance space with sound-reflective surfaces; the sound of reverberation is electronically added to the vocals of singers and to musical instruments. This is done in sound recordings by using effects units. Effects units that are specialized in the generation of the reverberation effect are called reverbs. Whereas reverberation adds to the naturalness of recorded sound by adding a sense of space, reverberation can reduce speech intelligibility when noise is present. Users of hearing aids report difficulty in understanding speech in reverberant, noisy situations. Reverberation is a significant source of mistakes in automatic speech recognition. Dereverberation is the process of reducing the level of reverberation in a signal. Reverberation time is a measure of the time required for the sound to "fade away" in an enclosed area after the source of the sound has stopped.

When it comes to measuring reverberation time with a meter, the term T60 is used. T60 provides an objective reverberation time measurement, it is defined as the time it takes for the sound pressure level to reduce by 60 dB, measured after the generated test signal is abruptly ended. Reverberation time is stated as a single value if measured as a wideband signal. However, being frequency dependent, it can be more described in terms of frequency bands. Being frequency dependent, the reverberation time measured in narrow bands will differ depending on the frequency band being measured. For precision, it is important to know what ranges of frequencies are being described by a reverberation time measurement. In the late 19th century, Wallace Clement Sabine started experiments at Harvard University to investigate the impact of absorption on the reverberation time. Using a portable wind chest and organ pipes as a sound source, a stopwatch and his ears, he measured the time from interruption of the source to inaudibility.

He found that the reverberation time is proportional to room dimensions and inversely proportional to the amount of absorption present. The optimum reverberation time for a space in which music is played depends on the type of music, to be played in the space. Rooms used for speech need a shorter reverberation time so that speech can be understood more clearly. If the reflected sound from one syllable is still heard when the next syllable is spoken, it may be difficult to understand what was said. "Cat", "Cab", "Cap" may all sound similar. If on the other hand the reverberation time is too short, tonal balance and loudness may suffer. Reverberation effects are used in studios to add depth to sounds. Reverberation does not alter the pitch. Basic factors that affect a room's reverberation time include the size and shape of the enclosure as well as the materials used in the construction of the room; every object placed within the enclosure can affect this reverberation time, including people and their belongings.

Reverberation time could only be measured using a level recorder. A loud noise is produced, as the sound dies away the trace on the level recorder will show a distinct slope. Analysis of this slope reveals the measured reverberation time; some modern digital sound level meters can carry out this analysis automatically. Several methods exist for measuring reverb time. An impulse can be measured by creating a sufficiently loud noise. Impulse noise sources such as a blank pistol shot or balloon burst may be used to measure the impulse response of a room. Alternatively, a random noise signal such as pink noise or white noise may be generated through a loudspeaker, turned off; this is known as the interrupted method, the measured result is known as the interrupted response. A two-port measurement system can be used to measure noise introduced into a space and compare it to what is subsequently measured in the space. Consider sound reproduced by a loudspeaker into a room. A recording of the sound in the room can be compared to what was sent to the loudspeaker.

The two signals can be compared mathematically. This two port measurement system utilizes a Fourier transform to mathematically derive the impulse response of the r

The Order of the Smile is an international award given by children to adults distinguished in their love and aid for children. The idea of the Order of the Smile was established in 1968 by the Polish magazine Kurier Polski, inspired by Wanda Chotomska. In 1979 the Secretary-General of the United Nations Kurt Waldheim recognized the Order. From the Order of the Smile became an international order. In 1996, in Rabka, the Order of the Smile Museum was established on the grounds of the family park known as "Rabkoland." After the region had been given the official status of the "City of Children from around the World," an initiative was put forward to open a permanent Polish Santa's Village, which would accept letters addressed to Santa Claus from children across Poland. In 2003 an International Charter of the Order of the Smile session took place outside the Warsaw headquarters in Świdnica, where the Child Friendship Center was being erected. Świdnica had been titled the "Capital of Children's Dreams," and September 21, 2003, was declared Order of the Smile Children's Day.

Chotomska's television series Jacek i Agatka announced a competition to submit a design for the Order of the Smile. The award's logo was developed by a nine-year-old girl from Głuchołazy, Ewa Chrobak. Using a plate as a template, she drew a sun, added uneven rays of light; the design, one of 45,000, submitted, was chosen by Szymon Kobyliński, who elaborated it into its current form. All candidates for the Order of Smile should be nominated by children. Nominations can come collectively from many children. Nominations can be submitted from all around the world; the candidates should work for children. Nominations should be sent to the International Chapter of the Order of Smile. Afterwards the candidates are chosen to be Laureates by the Chapter; the Order is awarded twice a year: in fall. Laureates of the Order of Smile include now about 1000 people from 50 countries; the medal -, a badge representing a smiling sun - is awarded in Warsaw, Poland by the International Chapter of the Order of the Smile.

There is a special procedure of the decoration. In special cases the decoration could be held in the country of the laurate; the right to use the title of the "Knight of the Order of Smile" is guaranteed only to those who were decorated at an official ceremony organized by the Chapter. Although most of the 59 members of the Chapter are of Polish descent, it includes representatives from other countries such as Azerbaijan, Argentina, Belarus, Canada, the Czech Republic, Georgia, Hungary, Israel, Japan, Romania, Serbia, Tunisia, the United Kingdom and the United States. At the forefront of the International Chapter of the Order of Smile stands the Chancellor, Marek Michalak, who remains in this position since 19 January 2007. Previous Chancellors include: Ewa Szelburg-Zarembina, Radoslaw Ostrowicz, Cezary Leżenski. On 16 November 1992, the International Chapter of the Order of Smile was registered in Poland as an association; some notable Knights and Dames to receive the Order of the Smile include: The youngest Knight to receive the Order of the Smile is Malala Yousafzai, awarded the order in 2016 aged 19.

The oldest was Irena Sendler in 2007, aged 97. Children's literature portal Official site of the Order of the Smile

Protect is a political organization established in 2002 and dedicated to the protection of children from abuse and neglect. It is a nonprofit 501 membership association with members in every U. S. state and 10 nations. Protect achieved great success in its first three years, winning legislative victories in eight state legislatures, it advocates a nonpartisan "pro-child, anti-crime" agenda, works with both conservative and liberal constituencies and lawmakers. Protect advocates a "pro-child, anti-crime" agenda, which combines traditionally liberal positions on child protection with traditionally conservative positions on crime. Protect's pro-child agenda includes legal advocacy for child victims and reform and adequate funding of child protective services, its anti-crime agenda includes stronger criminal sentencing and containment of released sex offenders and increased funding for law enforcement. Protect focuses its work on four principal campaigns: Circle of Trust Campaign: Since its creation in 2002, Protect has led successful legislative battles to eliminate laws that award preferential treatment to criminals who sexually assault their own children.

Protect's Circle of Trust campaign has fought to reform and strengthen laws in North Carolina, Illinois, Virginia and New York. Real Safety Campaign: Protect advocates intensive community supervision—or "surveillance and containment"—of convicted sex offenders released into communities; the Real Safety campaign educates the public and lawmakers about the dangers of relying upon sex offender registries and residency restriction laws to keep children safe, calling for long-term and lifetime probation and parole. Accountability Campaign: In 2006, Protect announced it was launching its Accountability Campaign to hold public servants accountable for their performance in combatting crimes against children. Child Pornography Campaign: In 2006, Protect launched a national anti-child pornography campaign. In 2005, the punk rock record label, Fat Wreck Chords released a charity record for Protect, entitled Protect: A Benefit for the National Association to Protect Children. NYDM, New York Death Militia, a worldwide metal music organization, sponsors metal music shows in support of Protect.

These shows are happening nationwide across the United States. 2011 Former child actress Alison Arngrim, a victim of sexual abuse, lobbies for and speaks for Protect. Child abuse Child pornography Child sexual abuse Incest Protect Child Sexual Abuse and the State by Ruby Andrew, UC Davis Law Review, vol. 39, 2006. Discusses U. S. incest laws in cases where victim is a minor. The Incest Loophole by Andrew Vachss, New York Times, Nov. 20, 2005. Sentencing incest perpetrators. Andrew Vachss speaks on the importance of Protect, "Family of Choice webcast," Jan. 14, 2009