Staffan Hygge Noise, memory and learning (Buller, minne och inlärning) Staffan Hygge Environmental Psychology Department of Building, Energy and Environmental Engineering Faculty of Engineering and Sustainable Development University of Gävle Bo i Ro, Stockholm Oct 20 th, 2015

Contents of my talk Text based reading and learning in noise Classroom experiments on noise and memory of a text A natural experiment on chronic aircraft noise and cognition in children (the Munich study) Laboratory experiments on noise and memory systems WHO – Burden of Disease from environmental noise Speech based listening and learning in noise or degraded speech Speech intelligibility, recall and memory – Signal-to- Noise Ratio (SNR) and Reverberation time (RT)

Classroom Experiments - Results

The Munich airport noise study on children's cognition

Children's cognition, some of the results Difficult word list Difficult paragraphs Long-term recall The Munich airport noise study on children

Laboratory experiments on noise and memory systems – Memory of the text

Laboratory experiments on noise and memory systems – Aggregated measures

Structural Equation Model Conceptual diagram of a modified Model M4 for a single sample with the addition of a separate 1st-order factor (Text) for the text memory items (RCLtxt, RCGtxt) loaded on the 2nd-order factor Episodic, with the corresponding indicators, standardized loadings, and free error covariances (  2 = 90.17, df= 74, p =.097, RMSEA =.028). Noise conditions did not significantly change the fit of the Structural Equation Model!

WHO, 2011 Chapter: Environmental noise and cognitive impairment in children

Three field studies combined Figure. Dose-effect curves from epidemiological field studies with chronic noise exposure Rd = Reading, Rcl = memory, recall 1 Recall, children, old airport, Hygge et al. (2002) - longitudinal 2 Recall, children, new airport, Hygge et al. (2002) - longitudinal 3 Reading, children, old airport, Hygge et al. (2002) - longitudinal 4 Reading, children, new airport, Hygge et al. (2002) - longitudinal 5 Reading, children, airport, Stansfeld et al. (2005) – cross-sectional 6 Free recall, children, road traffic, Lercher et al. (2003) – crosssectional 5 Rd 1 Rcl 3 Rd 4 Rd 2 Rcl 6 Rcl

EUR-A countries can be calculated (Table 3.3). The absolute DALY for the EUR-A countries, with an estimated total population of million, is therefore

Speech based listening and learning in noise or degraded speech Exploring how spoken information, in contrast to written information, is processed in working memory (WM) and mediated to long-term memory How much does SNR and RT influence recall and memory? Are the effects of SNR and RT additive or do they interact? Knowing more about their additive or interactive effects has both a theoretical and practical value.

Speech intelligibility and memory – Reverberation time and background noise Direct sound: The part of the sound that goes the shortest distance from speaker to listener Reflected sound: The part of the sound that reaches the listenser after having been reflected by different surfaces in the room. Reaches the ear later than the direct sound

Indoor sound pressure level as a function of the distance to the sound source -6dB with doubling distance Constant sound level Distance from source Sound pressure level, dB(A) Near field Reverberation field An example: When a teacher speaks at 66 dB(A), that level drops to  52 dB(A) 6 m out in an ordinary classroom. This is only 7 dB(A) above a background level of 45 dB(A)

A long reverberation time may disturb speech perception Reflected sounds that arrive later than ms after the direct sound interfere with the direct sound and disturb speech perception by masking the direct sound The largest and most critical masking effects are vowels that mask subsequent consonants, which have a lower sound level higher frequency, but are more important for speech intelligibility At the same SNR-level a shorter reverberation time therefore gives a clearer signal and better speech perception

Does reverberation time cause a problem in schools? Measurements and recordings in two classrooms – A short lecture A classroom with a long reverberation time s in the lower frequency bands Another classroom with a reverberation time around 0.3 s in all frequency bands Results: Means 2.16 (long RT) and 4.00 (short RT), F(1,17) = 16.60, p <.001

To hear but not remember Reverberation time (RT) and signal-to-noise ratio (SNR) Participants heard word lists and repeated the words directly Short RT (0.5 s) Long RT (1.2 s) Number of correctly recalled words p =.025 Conclusion: Fewer word are remembered after hearing them under them under a low signal-to-noise (SNR) ratio and a long reverberation time SNR 27 dB Good SNR 4 dB Bad p <.001

The role of Working Memory (WM) WM is employed for temporary storage of information, to elaborate the information, to link it together with information in long-term memory and to transfer the information to long-term memory WM has a limited capacity The more of that capacity that is taken up by identifying the words that are heard, the less is left for elaboration of the information, for stroring, and for memory and learning

Recent studies Recall of words spoken in the first and second language: Effects of signal-to-noise ratios and reverberation times for school children in grade 4 and College students

Free recall of words in wordlists Children Grade 4, N = 72, run as a group in their classrooms College students, N = 48, run individually in the lab with headphones and computer Signal-to-Noise ratio (SNR)+3 and +12 dB Reverberation time (RT)1.2 and 0.3 s Language (Lang) English and Swedish 12 wordlists in each language For children grade words in each list For college students - 12 words in each list Words with high ranks were taken from language specific category norms for 24 categories, which were sorted by Graeco- Latin squares into 24 lists with equal average ranks of the words Materials and Procedure

Examples of the words Swedish RT =1.2, SNR =+3 dB English RT =1.2, SNR =+12 dB Swedish RT = 0.3, SNR =+3 dB English RT =0.3, SNR =+12 dB The presentation orders of the lists were counterbalanced across experimental conditions and subjects Materials and Procedure

Total By Study Separate follow-ups Source Total Grade 4 College LangXX X Lang*StudyX SNRXXX SNR*StudyX Lang*SNRX Lang*SNR*Study X RT*SNRXX RT*SNR*Study (p = 0.063) Lang*RT*SNR*Study (p = 0.083) Results

For Grade 4 there is a more marked improvement with Swedish compared to English than for the College students Lang*Study

There is a larger gain in recall from +3 dB to +12 dB for Grade 4 than for the College students SNR*Study

Looking at the slopes, there are more marked increases in recall with improved SNR for Grade 4 than for the College students, and the most marked increase for Grade 4 is with the Swedish words Lang*SNR*Study

Looking at the slopes, there are more marked increases in recall with improved SNR for Grade 4 than for the College students, and the most marked increase for Grade 4 is with the Swedish words Lang*SNR*Study Increases Value:0.070 Ratio:1.172 Value:0.093 Ratio:1.278 Increases Value:0.131 Ratio:1.482 Value:0.110 Ratio:1.932

Recall - Improvement per SNR 5 dB, % Grade 4 English50.4 Swedish26.0 College English15.4 Swedish9.5 Relative improvement of recall with a +5 dB increase of SNR

Conclusions SNR is a stronger determinant of recall than RT is A SNR improvement to +12 dB from +3 dB is more important for Grade 4 than for College students, in particular for the Swedish words There are no strong indicators of an interaction between SNR and RT, and a long RT at SNR +3 dB may improve, not impair, recall