Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Humpback and minke whale acoustic presence with reference to fish sounds and ambient noise levels at Saba Bank, Caribbean Windward Dutch Islands
Risch, D. ; Haan, D. de - \ 2016
IMARES (Report / IMARES C067/16) - 22 p.
megaptera novaeangliae - whales - acoustics - sounds - netherlands antilles - monitoring - saba - walvissen - geluidsleer - geluiden - nederlandse antillen
The Antillean Island chain is a known breeding and calving ground for North Atlantic humpback whales (Megaptera novaeangliae). However, while most research efforts for this species have focused on the largest aggregation of whales, located on Silver Bank, off the northern coast of the Dominican Republic, there are still significant knowledge gaps with respect to humpback whale movements along the Antillean Island chain. Even less is known about the spatio-temporal distribution of other marine mammal and fish species in the region. This report summarizes analysis results of acoustic data (10-8000 Hz effective analysis bandwidth recorded at a 25% duty cycle), recorded on the north east of Saba Bank from October 2011 to April 2012. The results show the consistent presence of humpback whales in the vicinity of Saba Bank during their winter breeding season, occasional presence of minke whales and the presence of sound producing fish assemblages. Humpback whale song occurred from the end of December to the end of the recording period in April. From February to April humpback whale song was recorded on more than 89 % of all recording days, though it occurred most frequently in March. All recording days in March showed song presence, with an average of 8.5 ± 2.8 (mean ± SE) hours of recorded song per day. In contrast, for minke whale (Balaenoptera acutorostrata) 48 pulse trains (n = 32) were detected less frequently between February to April 2012. A variety of unidentified fish sounds were present throughout the recordings. Although the occurrence of these sounds was not quantified, notable fish choruses (e.g. grouper spp. Epinephelinae) consisting of one to two distinct pulsed calls in the frequency range of 100 - 600 Hz were documented from October to December 2011 in particular. The results of this pilot project highlight the feasibility of using passive acoustic monitoring (PAM) to explore year-round marine mammal and fish presence and distribution in otherwise understudied and remote field sites.
Radio en kleurige overalls helpen tegen verenpikken
Rodenburg, T.B. - \ 2015
WageningenWorld (2015)2. - ISSN 2210-7908 - p. 7 - 7.
hennen - kippen - verenpikken - diergedrag - stressfactoren - dierenwelzijn - geluiden - radio - kleur - diergezondheid - dierlijke productie - pluimvee - hens - fowls - feather pecking - animal behaviour - stress factors - animal welfare - sounds - colour - animal health - animal production - poultry
Wageningen University heeft samen met de Universiteit Utrecht en de Rijksuniversiteit Groningen manieren gevonden om verenpikken bij leghennen tegen te gaan. Dat biedt perspectief bij het verbod op snavelkappen dat in 2018 van kracht wordt.
Radio doet scharrelkip goed
Sikkema, Albert ; Haas, Elske de - \ 2014
chicken housing - feather pecking - poultry farming - animal welfare - animal behaviour - cannibalism - sounds - radio - animal health - animal production - poultry
Onderzoek naar de affecten van de aanleg van damwanden en grondverdichting op tandwalvissen in het Dolfinarium Harderwijk
Haan, D. de - \ 2013
IJmuiden : IMARES (Report / IMARES Wageningen UR C020/13) - 62
dammen - uitrusting - zeezoogdieren - dierentuindieren - simulatie - diergedrag - dierenwelzijn - geluiden - veluwe - walvissen - oscillatie - dams - equipment - marine mammals - zoo animals - simulation - animal behaviour - animal welfare - sounds - whales - oscillation
Voor het vaststellen van de effecten van de aanleg van damwandinstallaties en grondverdichting als onderdelen van het grootschalig bouwplan Waterfront Harderwijk van de gemeente Harderwijk werden op vijf verschillende locaties van het bouwplan installaties gesimuleerd en de geluidseffecten daarvan in vier verschillende bassins op het terrein van het dolfinarium simultaan gemeten. Het onderzoek naar de effecten van het trilgeluid was beperkt tot de bassins waar bruinvissen en tuimelaars werden gehouden. Omdat er tijdens de proeven sterke reacties van haaien en roggen in het roggenbasin werden waargenomen, zijn in dit rapport enkele mitigerende maatregelen voor deze diersoorten opgenomen.
Onderzoek naar de effecten van de aanleg van een 20 m-paalanker voor Mosselzaad Invang Installaties (MZI's) op zeezoogdieren
Haan, D. de; Burggraaf, D. - \ 2012
IJmuiden : IMARES (Report / IMARES Wageningen UR C140.11) - 80
zeehonden - phocoenidae - geluiden - geluid - akoestische emissie - seals - sounds - noise - acoustic emissions
Mosselzaad Invanginstallaties (MZI’s) in de Waddenzee en Oosterschelde worden opgehangen aan 20 m-paalankers, die met een trilhamer in de zeebodem worden gedreven. In het kader van het beheersplan voor de MZI-vismethode werden de effecten van de aanleg van een paalanker op zeehond en bruinvis bepaald. Een 20 m-paalanker werd met een trilhamer onder bedrijfsmatige condities in de zeebodem gedreven, terwijl het onder- en bovenwater ontwikkelde geluid op afstanden van 25 tot 1600 m van de trilhamer werd gemeten. De metingen vonden plaats op korte afstand van de MZI-locatie Vogelzand in de Waddenzee. Deze locatie werd gekozen vanwege de harde bodem, zodat het gemeten geluid onder de zwaarst mogelijke conditie is bepaald.
Technologieën voor non-destructieve detectiemethoden
Kogel, Willem Jan de - \ 2011
plant diseases - plant pests - detection - techniques - sounds - odours
Review of the spatial and temporal distribution by life stage for 19 North Sea fish species
Teal, L.R. ; Hal, R. van; Damme, C.J.G. van; Bolle, L.J. ; Hofstede, R. ter - \ 2009
IJmuiden : IMARES (Report / IMARES Wageningen UR C126/09) - 118
visserijbeheer - geluidsniveaumeters - gehoor - schadepreventie - zwemblaas - ontwrichting - milieueffect - geluiden - visserijbiologie - fishery management - sound level meters - hearing - loss prevention - swim bladder - disruption - environmental impact - sounds - fishery biology
Considering the increase in human activity in the North Sea, particularly cargo shipping and the rapidly expanding construction and operation of oil platforms and wind farms, as well as the continued use of the area for military purposes, fisheries and sand extraction, there is a growing concern about the potentially harmful impacts of such anthropogenic activities on marine life. Particular concerns have been raised about the effect of loud impulse sounds and high noise levels, which may affect marine animal life in different ways: habitat use, such as feeding and migration, and reproduction patterns may be disturbed. In the extreme case animals may suffer from sub-lethal or lethal physical damage such as hearing loss and disrupted swim ladders. Knowledge of the spatial distribution and seasonal patterns in the presence of different life stages of marine species is therefore critical for assessing to what extent the dispersion of marine life overlaps with the distribution of human activities and for estimating how potentially harmful impacts can be mitigated both spatially and temporally. The aim of this desk study is consequently to provide a concise overview of existing information on seasonal patterns in the dispersion of fish species in the North Sea, in particular by highlighting the knowledge gaps.
Liefdesliederen op zes poten
Dicke, M. - \ 2007
Natura 104 (2007)4. - ISSN 0028-0631 - p. 100 - 101.
insecten - communicatie tussen dieren - geluiden - insects - communication between animals - sounds
Uitleg over de rol van geluiden van krekels en muggen. Als partners binnen elkaars bereik zijn, veranderen de geluiden
Effects of sounds on North Sea fish species
Reijnders, P.J.H. - \ 2005
mariene ecologie - geluidsniveaumeters - geluiden - visziekten - vis - diergezondheid - marine ecology - sound level meters - sounds - fish diseases - fish - animal health
Study of the possible effects of anthropogenic underwater noise in the oceans on marine fish. The study determines the minimum sound levels of pure tones and noise at which some marine fish species begin to react
Ruimte, rust en stilte; beleving door burgers en indicaties voor beheer en beleid
Coeterier, J.F. ; Boer, T.A. de - \ 2001
Wageningen : Alterra (Alterra-rapport 423) - 80
landschapsbeleving - landschap - perceptie - geluiden - geluid - beleid - burgers - belevingsonderzoek - geluidshinder - maatschappijwetenschappen - omgevingspsychologie - landscape experience - landscape - perception - sounds - noise - policy - citizens
In een landelijke enqulte is het maatschappelijk belang van ruimte, rust en stilte vastgesteld. Hoewel deze kwaliteiten nog steeds te vinden zijn in het landschap, worden ze wel bedreigd. Rust en stilte worden verschillend ervaren: rust is meer innerlijk, stilte meer uiterlijk. Een gevoel van ruimte is niet gebonden aan openheid; je kunt het ook in een bos hebben. De beleving van ruimte hangt sterk samen met die van rust. Gebiedsvreemd lawaai, vervuiling en niet-passende elementen in het landschap doen afbreuk aan beide. Verschillende typen groene omgevingen hebben een eigen verwachting van ruimte, rust en stilte. Dit maakt beheer en beleid omgevingsspecifiek en de identiteit van een landschap een belangrijk beleidsuitgangspunt - identiteit zowel inruimte als in tijd gezien.
Gelderse stilte?; onderzoek naar de stiltebeleving van recreanten
Goossen, C.M. ; Langers, F. ; Vries, S. de - \ 2001
Wageningen : Alterra (Alterra-rapport 398) - 74
openluchtrecreatie - recreatie - geluidshinder - geluid - geluiden - perceptie - nederland - beschermde gebieden - kennis - gelderland - belevingsonderzoek - maatschappijwetenschappen - omgevingspsychologie - stilte - outdoor recreation - recreation - noise pollution - noise - sounds - perception - netherlands - reserved areas - knowledge
Via 190 interviews met wandelaars en fietsers is antwoord gekregen op de centrale vraag hoe recreanten stilte beleven in de provincie Gelderland. De interviews zijn in en nabij drie stiltegebieden gehouden. Tijdens het interview is het geluid ter plaatse gemeten. Het blijkt dat hoe hoger het gemiddelde geluidsniveau (Laeq) is, hoe lager de waardering voor het geluid. Jongeren blijken ook kritischer te zijn ten aanzien van de geluidswaardering dan ouderen. Andere factoren spelen geen rol bij de stiltebeleving. Tot circa 40 dB(A) is de waardering goed. Een geluidsniveau dat hoger is dan 50 dB(A) krijgt een zeer lage waardering.
The use of edge habitats by commuting and foraging bats
Verboom, B. - \ 1998
Agricultural University. Promotor(en): H.H.T. Prins; J. Veen. - Wageningen : IBN-DLO - ISBN 9789054858386 - 123
communicatie tussen dieren - geluiden - geluidsleer - dieren - voedingsgedrag - Chiroptera - verspreiding - windbescherming - windsingels - heggen - Nederland - diergemeenschappen - communication between animals - sounds - acoustics - animals - feeding behaviour - Chiroptera - dispersal - wind protection - shelterbelts - hedges - Netherlands - animal communities

Travelling routes and foraging areas of many bat species are mainly along edge habitats, such as treelines, hedgerows, forest edges, and canal banks. This thesis deals with the effects of density, configuration, and structural features of edge habitats on the occurrence of bats. Four hypothetical functions of edge habitats for bats were studied: foraging areas, shelter from wind, shelter from avian predators, and acoustical landmarks.

Both wind and food abundance were found to affect the occurrence of foraging pipistrelle bats, Pipistrellus pipistrellus, near treelines. Feeding activity of pipistrelle bats was positively related to height, width and foliage density of treelines. The preference by pipistrelle bats of commuting routes leading from the roost to foraging areas was explained by the distribution of potentially good feeding sites at close distance from the roost.

The results stress the importance of wind protected areas where bats can feed during windy conditions. Predator avoidance is argued to be a constraint on the movements of commuting bats at relatively high light levels, i.e. at dusk and dawn. Indications that vertical landscape elements play a role in the navigation by bats as acoustical landmarks come from a study where pond bats, Myotis dasycneme, commuting over canals gradually adapted their pulse emissions to the distance to the banks. Practical guidelines are provided to implement the results into the planning, conservation, and management of edge habitats for bats.

Analyse van de mate van geluidshinder op verblijfsaccomodaties; aantal overnachtingen per geluidszone in 1995 en in 2020
Goossen, C.M. - \ 1997
Wageningen : DLO-Staring Centrum - 41
lawaaibestrijding - geluidshinder - geluidsleer - geluiden - vibratie - geluid - controle - vrijetijdsactiviteiten - openluchtrecreatie - accommodatie - recreatie - statistiek - nederland - noise abatement - noise pollution - acoustics - sounds - vibration - noise - control - leisure activities - outdoor recreation - accommodation - recreation - statistics - netherlands
Onderzocht is hoeveel kampeer- en bungalowterreinen in 1995 in Nederland in bepaalde geluidszones liggen. De helft ligt in de geluidszone van minder dan 40 dB(A) en deze genereren 54% van alle overnachtingen. In de zone met minder dan 55 dB(A) ligt zelfs 85% van alle terreinen, met 92% van alle overnachtingen. Bij de geluidszones van 1990 van alleen (snel)wegen ligt 75% in de zone van minder dan 40 dB(A) met 76% van alle overnachtingen, en ligt 94% in de zone van minder dan 55 dB(A) met 96% van alle overnachtingen. Met drie scenario's is onderzocht hoe de situatie er in 2020 uitziet met de dan geldende geluidszones.
Evolutionary aspects of acoustic communication in Ribautodelphax planthoppers (Homoptera, Delphacidae)
Winter, A.J. de - \ 1994
Agricultural University. Promotor(en): R.J. Post. - S.l. : De Winter - ISBN 9789054852292 - 123
Auchenorrhyncha - ecologie - diergedrag - gewoonten - communicatie tussen dieren - geluiden - geluidsleer - evolutie - fylogenie - oorsprong - fylogenetica - Auchenorrhyncha - ecology - animal behaviour - habits - communication between animals - sounds - acoustics - evolution - phylogeny - origin - phylogenetics

Delphacidae (Homoptera), commonly referred to as planthoppers, are herbivores, which usually feed on grasses and sedges. During sexual behaviour males and females communicate by exchanging low-frequency vibrational signals, which are transmitted through the substrate, normally the host plant. This thesis deals with the acoustic behaviour of one planthopper genus, Ribautodelphax, where both male and females have been found to produce species-specific calls, which differ between species in temporal parameters. As in other planthoppers, the acoustic signals of males and females are rather different. Male calls are more complicated, and consist of at least two structurally different elements, a variable number of 'chirps', followed by a 'buzz' of variable length, hence termed the 'chirp-section' and the 'buzz-section', respectively. The female call consists of a series of simple pulses, which differs between species in interpulse interval length ( IPI ), signal duration, and modulation of pulse repetition rate within the signal.
This study was aimed at answering the following central, interrelated questions:

1. Do planthopper calls have a function in species recognition (sexual isolation) and mate preference?
2. What forces have caused differentiation of acoustic signals?
3. What is the relationship between divergence in acoustic signals and speciation?.

It was confirmed that, during the first phase of the sexual behaviour (the socalled distant calling phase), these calls are especially important in bringing potential mating partners together. Males called first, and mating-receptive females responded acoustically. The male then started searching actively for the female and continued to exchange calls with her, during which the female remained sedentary until the male came in close range. Females only responded to conspecific male calls when they are virgin and old enough. In populations of two closely related species, the development of female responsiveness with age corresponded fairly well with that of insemination levels, which shows acoustic response levels to be good indicators of mating receptiveness.

At close range (courtship in the strict sense), males remained acoustically active, but the female signal length and calling frequency tended to decrease, and some females ceased responding altogether. This suggests that during courtship the male call serves in maintaining and enhancing the female's receptiveness, and that the female call is less important. At this stage of sexual behaviour females appeared to be rather cautious, and usually only allowed copulation after many refusals. Courtships were clearly shorter when a female was confined with two males instead of one. Females seemed not to mate randomly with the available males, leaving open the possibility of some form of sexual selection. In the absence of other obvious cues, it seems possible that females might prefer males on the basis of their acoustic signals, but possibly due to the limited number of observations no trend in preference was found. However, females did not actively choose between males, nor did males behave in any way aggressively towards each other. After both males called initially, usually only one male continued courtship, leaving the possibility that males first assess their relative attractiveness or social status m their calls.

Different closely related Ribautodelphax species performed the same behaviours during courtship, but differed more or less in the frequencies of transitions between behavioural events. A more distantly related species deviated more strongly in transition frequencies, as well as by exhibiting a behavioural element not shared by the other species.

Many combinations of Ribautodelphax species are known to be able to produce viable and fertile interspecific hybrids under no choice conditions. However, when both conspecific and heterospecific partners are available, interspecific matings rarely take place, if at all. After rearing two species together for 10 generations no indication was found of introgression having occurred. Thus, recognition of conspecifics takes place before mating. Most females exposed to playbacks of heterospecific male calls responded about as well as to conspecific calls. In contrast, males were found to approach only playbacks of conspecific female calls, or, in a two- way choice experiment, chose significantly more often for the conspecific call. In an additional experiment males were continously exposed to either a conspecific or a heterospecific female playback call during their development from egg to adult. After this treatment both types of males preferred the conspecific female call over the heterospecific one, but males with experience of the conspecific call did this significantly more often. Males primed with the heterospecific female call performed similarly to acoustically naive males. This shows that recognition of conspecific female signals by males is largely genetic, but can be improved to some extent by previous experience of the conspecific signal, whereas the recognition mechanism is not affected by heterospecific signals. Thus, the acoustic communication between the sexes forms at least part of the specific mate recognition system of these species. Apparently, species recognition in Ribautodelphax results primarily from the male preference for conspecific female calls. This is a surprising result, because females only mate once during their lives, in contrast to males. In the absence of any obvious male parental investment, apart from costs involved in searching, the females would be expected to be more selective.

At close range, most interspecific courtships observed did not result in copulation, which is likely to be a by-product of within-species choosyness by females towards acoustic or non- acoustic performances of males. Such interspecific encounters are unlikely to occur under natural conditions, because at that stage recognition has already taken place.

Artificial bi-directional selection for large and small IPI s in the female call of R. imitans was very successful, resulting in non-overlapping distributions of the character after only five generations. The mean of realized heritability estimates of all selection lines over this period was above 80%, and still above 50% over 10 generations. IPI proved to be a polygenic character, controlled by at least six independently segregating genetic factors. Other female call characters, like signal duration, and modulation of pulse repetition rate within the signal exhibited correlated responses. After the experiment a significant degree of symmetrical assortative mating was found in mate preference tests between males and females from oppositely selected lines, but co-selected males did not show a significant preference for female playback calls with IPI s close to those occurring in their selection lines. Some characters of the chirp-section of the male call also appeared to exhibit a correlated change, suggesting that male and female call characters do not evolve independently. It seems possible that the assortative mating among individuals of the selection lines is due to female preference for the changed male call parameters, rather than to the preference of males for changed IPI s in the female calls.

The genetic control of male call characters in R. imitans was studied by father-sons regression. Heritability estimates of the chirp-section characters were statistically significant (0.44-0.54), in contrast to those of the buzz-section (0.09-0.28). Phenotypic, genetic, and environmental correlations calculated among male call characters suggest that chirp-section and buzz-section characters vary independently. One chirp-section character, number of chirps, appeared to be influenced by sex-linked loci. This means that the heritability estimate obtained by father-sons regression probably underestimates the true heritability of this character.

The possibility that the calls have evolved as adaptations to prevent hybridization (reinforcement) appears to be unlikely, for reasons like the apparent genetic plasticity of call characters, the observation that females inseminated by heterospecific males produce both viable and fertile offspring, and the fact that these species live ecologically isolated. It seems more probable that the calls obtained their species-specificity as the result of selection and chance, e.g. after founder events. Potentially, sexual selection might also have contributed to the differentiation of at least the male call. In view of the genetic correlation between some male and female call characters found in R. imitans, the possibility that change in the call of one sex might affect that of the other cannot be excluded.

The observation that, during distant calling, males are much more selective than females with respect to calls of other species appears to be best explained from the need to to be as efficient as possible in finding a proper conspecific mate. Because Ribautodelphax species are confined to different host plants, the chances of meeting other related species are slim, and selection for precise species recognition is likely to be weak. In order to attract as many as possible males to chose among, it might be sufficient for females to recognize the calls of congenerics, which have basically the same structure. For males precise recognition is likely to be more important. There are usually less mating-receptive females than males present in a population, because females mate only once during their lives, in contrast to males. Tuning to a specific call type would increase the chances of finding as many as possible attractive females, as the fraction of such females (i.e. presumably those with call characteristics close to the population mean), is likely to decrease as the season progresses. In species living syntopically on the same host plant, females might be expected to be at least as selective as males towards heterospecific calls of the other sex, because that would seem to be the most economic and safe way to avoid heterospecific encounters. In two species of the planthopper genus Prokelisia, which share the same hostplant, this indeed seems to be the case.

In populations of two Ribautodelphax species, where diploid males and females live associated with triploid gynogenetic females, a peculiar use of the acoustic communication system in a within species context appears to occur. The triploids occasionally arise spontaneously in diploid populations, and need to mate with diploid males, but produce only identical triploid females. Because of their two-fold reproductive advantage, triploids potentially can outcompete the diploid females, which would also lead to their own demise. However, the ratio diploid: triploid females in the field was reported to be stable over time. A model is suggested explaining this stable coexistence by a dynamic 'armsrace' involving the female calls, enabled by the genetic plasticity of the female call, and driven by the selection pressure on males to prefer female calls deviating from the population mean, thereby avoiding mating with the otherwise indistinguishable triploids. This would also explain the peculiar occurrence of several different female call types within and between populations of the species in which such triploids occur.

In view of the potential effect of acoustic signals in species recognition, the evolution of the acoustic communication system might be the primary force behind speciation in planthoppers. However, a confounding factor in Ribautodelphax is that, although the species studied live potentially sympatrically, each is confined to one particular host plant species, on which they feed and oviposit and therefore are unlikely to meet related species in the field. Hence, call differentiation could have taken place as the result of isolation after a change to a new host. However, comparative evidence from related genera shows that acoustic differentiation can also occur without a host plant shift. It therefore seems inevitable to conclude that the change of the acoustic communication system in allopatry is indeed the main factor in planthopper speciation. Although speciation will be facilitated by a host plant shift, because it obstructs secondary contact, it appears to be no prerequisite. Species of genera living syntopically on the same host appear to have developed more rigid recognition systems than members of genera which are ecologically or geographically isolated, because interspecific inseminations were reported to be extremely rare or non-existent, even under no-choice conditions. In these species the specific mate recognition system has apparently changed sufficiently in allopatry to enable coexistence with congenerics after secondary contact. The process of speciation is viewed as undirected change of the specific mate recognition system in small isolated populations up to the point where other populations are no longer recognized, which is in accordance with Paterson's recognition species concept, except that the mate recognition system, at least some of its components, appears to be less evolutionary stable than envisaged by that author.

Sound absorption at the soil surface
Janse, A.R.P. - \ 1969
Wageningen University. Promotor(en): C.W. Kosten; A.C. Schuffelen. - Wageningen : [s.n.] - ISBN 9789022001790 - 215
bodemstructuur - bodemdeeltjes - grondanalyse - geluidsleer - vibratie - geluiden - bodemlucht - reflectie - resonantie - meting - onderzoek - bodemkunde - bodemfysica - grondmechanica - wetenschappelijk onderzoek - wetenschap - soil structure - aggregates - soil analysis - acoustics - vibration - sounds - soil air - reflection - resonance - measurement - research - soil science - soil physics - soil mechanics - scientific research - science
The properties of a soil structure may be examined in various manners. As well as a study of the stability, a knowledge of the geometry of the volume of air filled pores is often needed. The most common measurements, like those of porosity and flow resistance to gases do not permit a detailed description of this pore volume. Since wave phenomena are characterized by three independent variables, viz. frequency, amplitude and phase, with frequency chosen freely, the measurement of acoustical characteristics of the air in the soil offers new opportunities. Also a determination of the acoustical properties of a porous material is non-destructive.

In chapter 1, a description is given of an interferometric method of measurement following the derivation of the wave equation. The propagation velocity of sound in air and the specific mass of air are the important physical quantities. The change in these quantities is studied from variations in the experimental conditions, such as temperature and humidity. Next the principles of the propagation of sound in porous materials are presented. For a sample of thickness l and having a rigid backing, the specific acoustic impedance Z at the free surface is given by Z = W m coth(γ m l), where γ m is the propagation constant for acoustical waves in the sample and W m is the specific acoustic wave impedance. Z, W m and γ m are complex quantities. Z may be measured in an interferometer and W m and γ m characterize the sample material. γ m and W m considered as functions of frequency give more information on pore geometry than may be obtained from static measurements. The loci of the function in two types of a complex plane is studied. Finally the behaviour of this function in the complex planes is shown with some examples.

Chapter 2 contains a discussion of the measuring equipment used and of the calibration of the measuring set-up. After a discussion of the measuring techniques, the sources of error are evaluated.

Chapter 3 deals with the propagation of waves in porous materials. Independent determination of W m and γ m proves impossible for soil samples. A method for this, described in the literature, is rejected on the grounds of inadequate accuracy. An alternative approach is followed: the material is described by a mathematical model and the parameters in the model are considered as the characteristic quantities for pore geometry. The models assume comparatively simple geometries and may be considered an extension of the work of previous authors. In addition a new projection plane for the determination of γ m and W m by a graphical method is discussed. Use of the plane is confined to cases where the sample thickness may be varied. Also, formulas are derived with which the acoustical properties of prismatic of structures soils can be studied. Finally, the applicability of scale rules and the possibility of an electric- acoustical equivalent network are examined for the sample material. Neither approach seems promising.

Chapter 4 starts with a discussion of the problems to be expected on the com parison of calculated and measured curves for Z. Somes series of measurements are discussed. The mathematical models selected yield a reasonably good relation ship between the theoretical and measured values. A short critical discussion is given on the feasibility of an extension of the mathematical model.

In conclusion a brief discussion is devoted to measurements on layers whose solid phases can no longer be considered as rigid, such as layers of mulch and straw. Some results obtained with straw are dealt with.

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