Many sources give different recommendations for background noise levels. Due to the differences in the recommendations, it is important to understand the basis of the recommendations, how to interpret the recommendations, and what actions to take.
The sound pressure level is measured at a known distance from the source and reported in decibels (dB). For example, conversational speech is typically considered to be 60 dB at a 1-meter distance from the talker. If the measurement were taken at a different distance from the person speaking, the level would change. For example, doubling the distance in a wide-open environment will decrease the measurement by 6 dB.
Background noise measurements are intended to capture the average level of ambient noise in a space. Ambient noise includes the noise generally heard from the following sources:
- Building HVAC systems
- Fan noise from computers, displays, projectors, and other devices
- All other sources of sound that are heard when the space is free of people
Most often the background noise measurement is taken from several distinct positions in a room and averaged.
When using a sound meter to determine the background noise level in a room, many weightings are used for different situations. This article references A-weighting, which is the sound meter weighting that focuses on the frequency range where the human ear is most sensitive.
Signal to noise ratio
The ratio of speech compared to the background noise is a key factor in ensuring signal comprehension. This is the signal-to-noise ratio. Industry guidelines describe the minimum signal-to-noise ratio for conference room spaces to be in the order of 20 dB. So, if a person spoke at a 60 dB SPL A-weighted level, then the room should ideally have a background noise level of no more than 40 dB SPL A-weighted.
Vocal effort is related to distance, noise & room properties. Noise levels being equal, people in smaller rooms are closer and require less vocal effort. In larger rooms, people are farther away, so more vocal effort (higher level) is required to maintain an adequate SNR for distant listeners.
In a smaller room people are generally closer together and can have softer conversations than when in a large room. In a smaller space, the conversation decibel level is often lower than the referenced 60 dB. Due to this, smaller spaces should have an appropriate SNR to support these quieter conversations. An example is if a person is speaking at 54 dB SPL A-weighted, then the room would ideally be no more than 34 dB SPL A-weighted.
In larger rooms, people are farther apart and tend to speak louder. This does not mean that the background noise level can be higher. The amplitude of the speech, the signal, decreases as it travels through the room while the background noise remains the same. To maintain an adequate SNR the background noise level still needs to be approximately 20 dB lower than the signal, or speech. If a person were to be speaking at a level of 65 dBA measured at 1 meter in free space, the measured level at 4 meters away would be 53 dBA. In this case, an ideal background noise level would be 33 dB to support easy listening and to prevent the person speaking from having to raise their voice even more.
Measuring background noise levels
Nureva devices measure background noise differently than a single measurement capture used by generic sound level meters.
Our audio devices utilize Microphone MistTM technology and take the quietest reading found in a 1-minute period from continuous 500-millisecond captures. This is done over 5 minutes and then the values are averaged. For every minute that moves forward, the average is based on the last 5 minutes. This captures the essence of the background noise. It attempts to omit speech events or sounds that are not consistently there.
Similar values can be obtained with a data-logging sound level meter as follows:
- Set the sound level meter to capture values over a 1-minute period
- Log the slow response, A-weighted minimum value
- Repeat and average the results for 5 minutes
Acceptable background noise levels
Nureva advises a maximum background noise level of around 40 dBA. If Nureva Console is reporting a background noise level beyond 45 dBA for a sustained period, it is recommended that steps be taken to review the room and potentially take action to improve the level.
Improving background noise levels
If excessive background noise is reported from within the room, the following causes should be investigated.
- Ensure that your microphone and speaker bar are not installed too close to equipment with a fan or fans
- Check the HVAC system and/or ventilation fans to see if the noise can be reduced through system maintenance or settings changes
- Check other electronics in the room for fan noises and move them into cabinets
- Check neighboring spaces for equipment that generates loud noise
If excessive background noise is coming from outside the room, sound dampening might be required.
Vyanzo vingi hutoa mapendekezo tofauti kwa viwango vya kelele za nyuma. Kwa sababu ya tofauti katika mapendekezo, ni muhimu kuelewa msingi wa mapendekezo, jinsi ya kutafsiri mapendekezo, na ni hatua gani za kuchukua. Kiwango cha shinikizo la sauti hupimwa kwa umbali unaojulikana kutoka kwa chanzo na kuripotiwa katika decibels (dB). Kwa mfano, sauti ya mazungumzo ni kawaida 60 dB katika umbali wa mita moja kutoka kwa msemaji. Ikiwa kipimo hicho kingechukuliwa kwa umbali tofauti na yule anayesema, kiwango hicho kingebadilika. Kwa mfano, mara mbili umbali katika mazingira wazi sana itapunguza kipimo kwa 6 dB. Vipimo vya kelele za nyuma vinakusudiwa kukamata kiwango cha wastani cha kelele za mazingira katika nafasi. Sauti ya mazingira ni sauti inayosikika kutoka kwa vyanzo vifuatavyo: - Mifumo ya HVAC ya Jengo - Sauti ya mashabiki kutoka kwa kompyuta, maonyesho, projectors, na vifaa vingine - Vyanzo vingine vyote vya sauti vinavyosikika wakati nafasi ni huru ya watu - Mara nyingi kipimo cha kelele ya nyuma huchukuliwa kutoka kwa nafasi kadhaa tofauti katika chumba na wastani. Wakati wa kutumia kipima sauti kuamua kiwango cha kelele ya nyuma katika chumba, uzito wengi ni kutumika kwa ajili ya hali tofauti. A-weighting ni kipimo cha sauti ambacho kinazingatia masafa ya sauti ambayo sikio la binadamu lina hisia zaidi. Signal kwa kelele uwiano uwiano wa hotuba ikilinganishwa na kelele ya nyuma ni jambo muhimu katika kuhakikisha ishara uelewa. Hii ni uwiano wa ishara-kwa-sauti. Miongozo ya sekta ya kuelezea kiwango cha chini cha ishara-kwa-sauti uwiano kwa ajili ya nafasi ya mikutano chumba kuwa katika utaratibu wa 20 dB. Kwa hiyo, ikiwa mtu alizungumza kwa kiwango cha 60 dB SPL A, basi chumba hicho kinapaswa kuwa na kiwango cha kelele ya nyuma ya si zaidi ya 40 dB SPL A. Jitihada ya sauti inahusiana na umbali, kelele na mali ya chumba. Viwango vya kelele vikiwa sawa, watu katika vyumba vidogo wako karibu zaidi na huhitaji jitihada kidogo za sauti. Katika vyumba vikubwa, watu wako mbali zaidi, kwa hiyo jitihada zaidi za sauti (kiwango cha juu) zinahitajika kudumisha SNR ya kutosha kwa wasikilizaji wa mbali. Katika chumba kidogo watu kwa ujumla ni karibu zaidi pamoja na wanaweza kuwa na mazungumzo laini kuliko wakati katika chumba kikubwa. Kwa mfano, katika maeneo ya chini, kiwango cha decibel cha mazungumzo ni chini ya 60 dB. Kwa sababu hii, nafasi ndogo zinapaswa kuwa na SNR inayofaa kusaidia mazungumzo haya ya utulivu. Kwa mfano, ikiwa mtu anazungumza kwa uzito wa 54 dB SPL A, basi chumba hicho hakitakuwa na uzito wa 34 dB SPL A. Katika vyumba vikubwa, watu wako mbali zaidi na huwa wanazungumza kwa sauti kubwa zaidi. Hii haina maana kwamba kiwango cha kelele ya nyuma inaweza kuwa ya juu. Kiasi cha hotuba, ishara, hupungua inapopita katika chumba hicho huku kelele za nyuma zikiwa sawa. Kwa hivyo, kwa kiwango cha juu cha SNR, kiwango cha kelele ya nyuma lazima iwe chini ya dB 20 kuliko sauti ya sauti. Ikiwa mtu anaongea kwa kiwango cha 65 dBA, kipimo cha mita moja katika nafasi ya bure, kiwango cha kupimwa kwa mita nne itakuwa 53 dBA. Kwa mfano, kiwango cha sauti ya nyuma ya 33dB ni muhimu kwa ajili ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti. Kupima viwango vya kelele ya nyuma Vifaa vya Nureva hupima kelele ya nyuma tofauti na kukamata kipimo kimoja kinachotumiwa na mita za kiwango cha sauti za kawaida. Vifaa vyetu vya sauti hutumia teknolojia ya Microphone Mist na kuchukua usomaji wa utulivu zaidi uliopatikana katika kipindi cha dakika moja kutoka kwa kukamata kwa kuendelea kwa milisekunde 500. Hii ni kufanyika zaidi ya dakika tano na kisha maadili ni wastani. Kwa kila dakika inayoendelea, wastani hutegemea dakika tano zilizopita. Hii inashika kiini cha kelele za nyuma. Inajaribu kuondoa matukio ya usemi au sauti ambazo hazipatikani kwa ukawaida. Kwa mfano, kwa mfano, kipimo cha sauti cha sauti cha sauti cha sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti ya sauti. Ikiwa Nureva Console inaripoti kiwango cha kelele ya nyuma zaidi ya 45dB kwa kipindi cha muda mrefu, inashauriwa kuchukua hatua za kukagua chumba na uwezekano wa kuchukua hatua za kuboresha kiwango. Kuboresha viwango vya kelele ya nyuma Ikiwa kelele ya nyuma kupita kiasi inaripotiwa kutoka ndani ya chumba, sababu zifuatazo zinapaswa kuchunguzwa. - Hakikisha kwamba kipaza sauti yako haijawekwa karibu sana na vifaa vyenye mashabiki - Angalia mfumo wa HVAC na au mashabiki wa uingizaji hewa ili kuona ikiwa kelele inaweza kupunguzwa kupitia matengenezo ya mfumo au mabadiliko ya mipangilio - Angalia vifaa vingine vya elektroniki katika chumba kwa kelele za mashabiki na uhamishe kwenye kabati - Angalia nafasi za jirani kwa vifaa vinavyotokeza kelele kubwa.