question: why do two sounds of the same volume create a louder noise together?
comment: Sound is essentially air compressed together in a pulse. This is why when looking at a speaker playing music it bounces - it "hits" the air, thus compressing it. So essentially, it is the force of the speaker on the air that makes up the sound. If you have two speakers you also exert more force on the air, thus make it louder. Same with the human voice, so ten thousand people have a lot more combined force from their vocal cords than ten people. In other words, ten thousand people produce more energy than ten are capable of. A side note, one more person does not equal double the volume. Assuming the people all have identical vocal cords, lungs etc. (like two identical speakers) it would take 10 to double the loudness humans perceive, and then 100 to double it again, 1000 to double it again and so on.
passages: Wallach et al. did not systematically vary the intensities of the two sounds, although they cited research by Langmuir et al. which suggested that if the second-arriving sound is at least 15 dB louder than the first, the precedence effect breaks down.
  
  The "Haas effect" derives from a 1951 paper by Helmut Haas.
   Section::::Amplitude difference.
   Section::::Relevance to sound level measurement and noise measurement.
   Cherry conducted attention experiments in which participants listened to two different messages from a single loudspeaker at the same time and tried to separate them; this was later termed a dichotic listening task. His work reveals that the ability to separate sounds from background noise is affected by many variables, such as the sex of the speaker, the direction from which the sound is coming, the pitch, and the rate of speech.
   Additionally, Wallach et al. demonstrated that when successive sounds coming from sources at different locations were heard as fused, the apparent location of the perceived sound was dominated by the location of the sound that reached the ears first (i.e. the first-arriving wavefront). The second-arriving sound had only a very small (albeit measurable) effect on the perceived location of the fused sound. They designated this phenomenon as the "precedence effect", and noted that it explains why sound localization is possible in the typical situation where sounds reverberate from walls, furniture and the like, thus providing multiple, successive stimuli. They also noted that the precedence effect is an important factor in the perception of stereophonic sound.
   Convolution and related operations are found in many applications in science, engineering and mathematics.
  
  BULLET::::- In image processing
  
  BULLET::::- In digital data processing
  
  BULLET::::- In acoustics, reverberation is the convolution of the original sound with echoes from objects surrounding the sound source.
   Interference is the addition of two or more waves that results in a new wave pattern. Interference of sound waves can be observed when two loudspeakers transmit the same signal. At certain locations constructive interference occurs, doubling the local sound pressure. And at other locations destructive interference occurs, causing a local sound pressure of zero pascals.
  
  Section::::Wave properties.:Standing wave.
   The first research on the topic of how the ear hears different frequencies at different levels was conducted by Fletcher and Munson in 1933. Until recently, it was common to see the term "Fletcher–Munson" used to refer to equal-loudness contours generally, even though a re-determination was carried out by Robinson and Dadson in 1956, which became the basis for an ISO 226 standard.
  
  It is now better to use the generic term equal-loudness contours, of which the Fletcher-Munsons curves are now a sub-set, and especially since a 2003 survey by ISO redefined the curves in a new standard.
  
  Section::::Experimental determination.
   BULLET::::- sound pressure level and
  
  BULLET::::- distortion of the sound reinforcement system
  
  Section::::Noise levels and reverberation.
   In air conditioning, the Coandă effect is exploited to increase the throw of a ceiling mounted diffuser. Because the Coandă effect causes air discharged from the diffuser to "stick" to the ceiling, it travels farther before dropping for the same discharge velocity than it would if the diffuser were mounted in free air, without the neighbouring ceiling. Lower discharge velocity means lower noise levels and, in the case of variable air volume (VAV) air conditioning systems, permits greater turndown ratios. Linear diffusers and slot diffusers that present a greater length of contact with the ceiling exhibit a greater Coandă effect.
   Section::::Creation of impulse responses.:Sine sweep method.
  
  Another technique, referred to as the sine sweep method, covers the entire audible frequency range, which can result in a broader-range, and higher-quality, impulse response. This involves the use of a longer sound to excite a space (typically a sine sweep), which is then put through a process of deconvolution to produce an impulse response. This approach has the advantage that such sounds are less susceptible to distortion; however, it requires more sophisticated processing to produce a usable impulse response. 
  
  Section::::Creation of impulse responses.:Maximum Length Sequences.
   The beating and roughness sensations associated with certain complex signals are therefore usually understood in terms of sine-component interaction within the same frequency band of the hypothesized auditory filter, called critical band.
  
  BULLET::::- Frequency ratios: ratios of higher simple numbers are more dissonant than lower ones ().
  
  In human hearing, the varying effect of simple ratios may be perceived by one of these mechanisms:
   Steven Feld (1994, p. 265-271), apparently in response to R. Murray Schafer's "schizophonia" and borrowing the term from Bateson, employs "schismogenesis" to name the recombination and recontextualization of sounds split from their sources.
  
  Section::::Concepts.:In modern warfare.
   Section::::Reception.
   These are audible most of the time and especially when the level of the original tone is low. Hence they have a greater effect on psychoacoustic tuning curves than quadratic difference tones.
  
  Quadratic difference tones are the result of
  
  F2 – F1
  
  This happens at relatively high levels hence have a lesser effect on psychoacoustic tuning curves.
  
  Combination tones can interact with primary tones resulting in secondary combination tones due to being like their original primary tones in nature, stimulus like. An example of this is
  
  3F1 – 2F2
   If the sound pressure "p" is measured at a distance "r" from the centre of the sphere, the sound pressure "p" at another position "r" can be calculated:
  
  The inverse-proportional law for sound pressure comes from the inverse-square law for sound intensity:
  
  Indeed,
  
  where
  
  BULLET::::- formula_26 is the convolution operator;
  
  BULLET::::- "z" is the convolution inverse of the specific acoustic impedance,
  
  hence the inverse-proportional law:
   Many older LEDE ("live end, dead end") control room designs featured so-called "Haas kickers" – reflective panels placed at the rear to create specular reflections which were thought to provide a wider stereo listening area or raise intelligibility. However, what is beneficial for one type of sound is detrimental to others, so Haas kickers, like compression ceilings, are no longer commonly found in control rooms.
  
  Section::::See also.
  
  BULLET::::- Binaural fusion
  
  BULLET::::- Franssen effect
  
  Section::::Further reading.
  
  BULLET::::- Floyd Toole "Sound Reproduction", Focal Press (July 25, 2008), Chapter 6
   Section::::Mechanisms of masking.
  
  There are many different mechanisms of masking, one being suppression. This is when there is a reduction of a response to a signal due to the presence of another. This happens because the original neural activity caused by the first signal is reduced by the neural activity of the other sound.
   Psychoacoustic experiments from the 1960s onwards tried to elucidate the nature of timbre. One method involves playing pairs of sounds to listeners, then using a multidimensional scaling algorithm to aggregate their dissimilarity judgments into a timbre space. The most consistent outcomes from such experiments are that brightness or spectral energy distribution , and the "bite", or rate and synchronicity and rise time , of the attack are important factors.
  
  Section::::Tristimulus timbre model.
   Section::::In music history.
   Mention is made of this on The Contrabass Shoppe web site which says...
   From the 2014 documentary "Beautiful Noise", Billy Corgan, on the long holocaust section played live, said:
  
  "It's one of those things where, it was full volume"br
  
  "and for the first three minutes it's like "oh okay this is kind of cool". "br
  
  "Then you're like "This is really too much. I wish they'd fucking stop"."br
  
  "And then at about 7 minutes it actually became kind of funny."br
  
  "And about 10 minutes in you start actually getting into it."br
  
  and Colm Ó Cíosóig interpreted audience reaction as:
   One principle for binding is based on the perceptual similarity between individual events. Sounds that share many or all of their acoustic features are more likely to have been emitted by the same source, and thus are more likely to be linked to form a “proto-object”. The other principle for binding is based on the sequential predictability of sound events. If events reliably follow each other, it is also more likely that they have a common underlying cause.
  
  Section::::Theoretical View.:Competition.
   BULLET::::- "A Snug Little Kingdom", "A Comedy of Bohemia" in three acts, was performed at the Royalty Theatre, running from 31 January to 28 February 1903 (28 performances). It featured Charles Warner, Lyn Harding and H. B. Warner.
   The electronic circuit that does this is called a compander and works by compressing or expanding the dynamic range of an analog electronic signal such as sound recorded by a microphone. One variety is a triplet of amplifiers: a logarithmic amplifier, followed by a variable-gain linear amplifier and an exponential amplifier. Such a triplet has the property that its output voltage is proportional to the input voltage raised to an adjustable power.
  