PROCEEDINGS of the
23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Experimental Design to Measure the Effect of Room Acoustics on
Prospective Memory of Hospital Nurses: A protocol
Jikke REINTEN1,2 ; Ella BRAAT-EGGEN2,3, Maarten HORNIKX2, Helianthe KORT1,2, Armin
KOHLRAUSCH2
1

University of Applied Sciences Utrecht, the Netherlands
2

Eindhoven University of Technology, the Netherlands

3

Avans University of Applied Sciences, the Netherlands

ABSTRACT
A prominent cognitive aspect of a hospital nurse’s job is to form, imprint and retrieve intentions forprospective memory (PM) tasks. During the verbal change of shift report and visual inspection of patient files,
generally performed in the nurses’ station at the start of a shift, important PM intentions are formed andimprinted. The correct retrieval of these intentions during the course of a shift is important for both patient
safety and satisfaction. The nurses’ station can be a hectic environment with multiple conversations at thesame time. While research has shown that the acoustic environment, speech in particular, has a significant
influence on several cognitive tasks, its effect on PM is not known. The acoustic environment of a nurses’
station potentially influences the forming and imprinting of PM intentions. The current paper presents thedesign of an ecologically valid experiment with the goal of measuring the effect of realistic backgroundspeech and room acoustic conditions on the forming and imprinting of prospective memory intentions. Whilethe experimental design is closely linked to a hospital situation, understanding the effect of acoustic
conditions on PM might also be valuable in other domains.
Keywords: Cognitive performance, Hospitals, Nursing, Room Acoustics, Experimental design

1. BACKGROUND
Nurses working in a hospital ward share a great responsibility: the wellbeing of their patients. The
sound environment they work in should facilitate them through minimalizing the risk of careomissions. Most importantly this regards patient safety and patient satisfaction, but it also touches
upon job satisfaction. The effect of the sound environment on cognitive performance has been
demonstrated in numerous studies, for reviews see (1,2). There is, however, a difficulty in translatingthese results to applied settings, as the effect of sound on performance is different for different
cognitive abilities (3), and dependent on the difficulty of the task (4). Furthermore, both the nature of
the sound environment (the room acoustics of the space in which the sound is produced and the exact
location from which the sound is originating) and the nature of the sounds that are produced have to betaken into account (3). Therefore, in order to determine whether and which aspects of the soundenvironment influence the task performance of a nurse we need to take a closer look at the nursing job
and the ward environment.
A nurse working in a hospital ward has to remember to perform several activities at the rightmoment. Typical examples are to administer antibiotics at a specific time, to call a family member ofa patient once they wake up or turning off a nebulizer after 10 minutes of use. Forgetting to executesuch tasks can in some occasions be a risk for a patient’s health or safety, in other occasions it could
have an effect on the patient’s satisfaction with the received care. Remembering to perform apreviously planned action requires prospective memory (PM) (5,6), a cognitive ability of which theeffect of sound on its performance, to our knowledge, has not yet been reported in literature.
A PM task comprises three aspects that can be distinguished. First, an intention has to be formed
to perform a future action. Second, this intention has to be encoded and third, the intention has to be
retrieved at the right moment, the window of opportunity. Most research on PM focusses on themaintenance of the intention during the delay between forming and retrieving, and on factors

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influencing successfully retrieving the intention, such as age or brain damage (7,8). In a typical PM
paradigm experiment, participants are instructed to work on a single simple ongoing task, such as
watching a video or processing written text from a screen. They are instructed to perform a PM task,for example to hit a key on the keyboard, either at a specific time (time -based PM task), or when acertain event occurs (event-based PM task). The event in the event-based PM task could be
encountering a specific word on a screen during a reading task, or seeing an animal in the case of thevideo task. The instructions for these simple PM tasks are presented prior to starting the ongoing task
and do not require any active planning from the participant. Only a limited amount of studies were
found that do take into account the forming and encoding of PM intentions, their results however dosuggest that the quality of the planning phase is important for PM performance (9,10).
Based on an observation study by the authors a division of activities in a nurses’ shift was made.
Typically, the first 15-30 minutes of a shift were spent reading patient files and receiving a verbal
change of shift report from a colleague. In this time period an important cognitive task is to form andencode intentions for PM tasks. No intentions have to be retrieved yet.
We argue that intentions which are not formed, or not properly formed are less likely to be executed,
and intentions which are not sufficiently encoded are less likely to be retrieved. The remainder of theshift is spent executing routine nursing tasks (medication round, ADL(activities of daily living) careand visiting round) during which intentions for specific PM tasks have to be retrieved and intentions
for new PM tasks are formed.
The first part generally takes place in a nurses’ station or an office where nurses walk in and out,
chat, discuss patients and exchange change of shift reports (occasionally multiple verbal reports
between different people at the same time). Additionally, a nurses’ station can be quite reverberant due
to large glass surfaces to allow a view of the ward. Based on the observation by the authors,
background speech is the most prominent sound source in the nurses’ station and will therefore be afocus of the current study, as well as room acoustic parameters.
Background speech has a significant effect on various cognitive tasks such as serial recall (11),proof reading (12) and mental arithmetics (11,13), but the effect on PM performance is unknown.
While there is much debate concerning the mechanisms responsible for the different effects -in a very
recent study, Bell and colleagues (14) present results contradicting the main assumption of theduplex-mechanism account which has, until now, received the most support- our main interest is toinvestigate whether realistic interventions regarding the sound environment influence a nurse’s work,
regardless of the mechanisms that are responsible. Moreover, reading patient files to form and encode
intentions is a complex task in which several coginitive abilities are employed. It requires semantic
abilities, taps into memory and has a planning component but the relative contribution of specificprocesses in unclear.
Considering speech as the most important sound source in a nurses’ station, we ask ourselves
whether the presence of speech, and the room acoustic design, which influences not only speech
intelligibility, but also the overall sound level and perception of the soundscape, influences theforming and encoding of PM intentions. Increasing sound absorption in the space would increase
speech intelligibility, but, especially in the case of more people simultaneously speaking also reduce
the overall sound level.
Based on the observation mentioned before, the expected importance of the planning phase for PM
performance and the evidence in literature on the influence of the sound environment on cognitive
performance, the following hypotheses were formulated.
1. The sound environment in a nurses’ station influences the forming of PM intentions.
2. The sound environment in a nurses’ station influences the encoding of PM intentions.
This paper describes the design of an ecologically valid laboratory study in which the experimental
task resembles the cognitive task of a nurse and the sound conditions are exemplary for a typicalnursing ward. The main parameters of the sound environment that are taken into account in thisprotocol are the amount of sound absorbing materials and the presence of background speech.
The results of a first pilot study, intended to validate the resemblance of the experimental task andsound conditions to the actual working environment of a nurse, are pending and could lead to
adaptations of the proposed method.

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2. EXPERIMENTAL DESIGN
2.1 Study Design
The objective of the proposed experiment is to determine whether background speech and room
acoustic parameters in a nurses’ station have an effect on the forming and encoding of prospective
memory intentions for care activities of nurses working in a hospital ward. The forming and encodingof PM intentions are the dependent variables and will be measured. A full within-subjects design will
be used with the sound environment in which the task is performed as the most critical independent
variable. Other within-subjects variables are the type of PM task (event-based or time-based) and thepresentation of patient info (visual or aural). The experiment consists of two phases that represent thetwo parts of a nurses’ shift that were described in paragraph 1. In the first phase, the experimental task
resembles the nurses’ activities at the start of a shift, reading patient files and receiving a verbal
transfer report. Participants are subjected to different realistic sound conditions during this first phasein which the forming of intentions is logged and measured. The second phase is designed to measure
whether the formed intentions are retrieved at the correct moment and therefore properly encoded. In
this phase, no experimental sound conditions will be used. A withinsubjects design will be used inwhich the sound conditions and corresponding task scenarios are counter balanced.
Experimental Phase 1: Reading & Verbal Transfer
This part of the experiment was designed with the aim to have a close resemblance to reality, bothfor the experimental task and the sound environment. Screenshots of electronic medical records(EMR) are used to create a scenario of ‘currently’ admitted patients in the ward. The partic ipating
nurse is asked to browse through the patient files and plan their shift accordingly. Additional to thevisually presented patient information, a verbal change of shift transfer that refers to the patients ineach scenario is announced at some point during the first part.
The amount of patients that are within a nurse’s care depends on several factors such as the severityof their condition, hospital management and perhaps even cultural differences. While in theobservation, one nurse was responsible for up to five patients, the scenarios for the current experimentare consisting of three patients who are admitted in adjacent rooms in an orthopedic ward. The reason
for this is that not being able to actually see and talk to the patients introduces an extra difficulty. The
first author is allowed access to a scrambled electronic patient file system that is used in a Dutch
hospital for educational purposes. Screenshots were taken of a ward overview that showed all‘currently’ admitted patients on a date in the past. For each patient, screenshots of the available
information in the system up to the selected date were taken. Even though the personal information on
the screenshots was scrambled, all patient and staff names are removed from the screenshots a nd
replaced with random names. Using Matlab 2019a, a user interface is developed that allows navigating
through the screenshots in a controlled setting. Figure 1 shows an example of the interface. This
screenshot provides an overview of protocols and to-be-performed actions of one patient. As
mentioned, all staff names have been removed, the (scrambled) name of the patient was replaced witha random name and an avatar was created for the patient to provide some visual recognition later on in
the experiment. Since the interface was built from a screenshot, the original buttons do not function.
Purple buttons( providing a high contrast with the screenshot) were added to allow the participants tonavigate through the different screenshots.
The amount of possible intentions to be formed is similar for each set of patient files, but it isexpected that the amount of intentions that is actually formed varies across participants. The difference
between the amount of possible intentions in each scenario, and the amo unt of actually formed
intentions by the participants is the measure of formed intentions.
PM intentions that can be formed based on the EMR can be time based and event based. An
example of a time-based task is to administer antibiotics at 9.00, an example of an event-based task is
to discuss a rash on a patient’s skin when visiting the patient with the doctor. Another distinction thatcan be made are regular PM tasks and irregular PM tasks. A regular PM task is conducted every day forevery patient. This includes, amongst others, writing your (participant) name on the information board
when entering the room in the morning and asking for pain scores on a visual analogue scale. Irregulartasks are specific for a patient, such as taking a patient’s temperature, administering antibiotics or
performing a bladder scan. As the regular tasks are performed every shift and can be seen as part of aroutine, they are less likely to be influenced by the sound environment in which intentions are formed.
Therefore, in this experiment the PM tasks that have to be formed and encoded are limited to the7819

irregular PM tasks. This is made very clear in the instructions at the start of the experiment and is taken
into account in the design of the second part of the experiment. A maximum of fifteen PM tasks can beformed in each experimental patient scenario that is created by the EMR screenshots. These include
five time-based PM tasks and ten event-based PM tasks. Participating nurses are instructed to think out
loud during this part of the experiment, allowing the researcher to record and log the intentions that areformed.

Figure 1 – Example of the user interface created for experimental phase 1.
Experimental Phase 2: Virtual Shift
The aim of this second part of the experiment is to measure whether the formed intentions areproperly encoded and thus retrieved in the right window of opportunity. To this end, an existing PM
laboratory task called Virtual Week was transformed into a task called Virtual Shift. Virtual Wee k is aboard game, designed by Rendell and Craik (16) with the aim to develop a procedure that explicitly
measures PM performance with a close resemblance to every-day life. In the game, participants roll a
die and move around on the board according the outcome. The position on the board corresponds to thetime of day, and one circuit on the board represents the waking hours of one day. To complete the game,seven circuits (seven days) would have to be finished. While moving around on the board theparticipants encounter ‘event cards’ that represent typical daily activities such as meals or a shopping
trip. After picking up an event card, the participant is required to make a choice about that event. In thecase of a meal, the required choice could be the drink they have with the meal. Each virtual day, 10
event cards are picked up. Before the start of the game, and before each new circuit, instructions for
PM tasks are given to the participants. The PM tasks are to be executed at a specific time (marked on
the board), or when a certain event occurs. Examples are to take antibiotics at 9.00 am and to return abook to the library when going for groceries (event card). Virtual Week has proven to be a valid
measure of PM performance for various situations (17,18).
For the purpose of the current experiment, Virtual Week is transformed into a game called Virtual
Shift. Rather than a day, one circuit of the board corresponds to one hour of a nurses’ shift, and theevent cards are typical events that occur during a nurses’ shift. An important aspect of Virtual Shift isthat the events are linked to the intentions to be formed in the patient scenarios that are used in the firstpart of the experiment. The consecutive events can be seen as a narrative for the participants’ shift.
They inform the participant that they are starting their medication round, when they enter a patient’s
room and also include the regular PM tasks that are performed every day for each patient. The events
can be, but do not have to be linked to a to be performed PM task. An example of an event, translated
to English (Virtual Shift is in Dutch) is shown below. For each PM task, only one timeslot, or one event
provides the correct window of opportunity.
“You are entering room 2, in which mrs Balvert resides, to administer medication. You introduce
yourself and write your name on the whiteboard in the room. Then you ask about her sleep quality andwhether she is in pain. Mrs. Balvert tells you that she has slept OK and that, as yesterday, she is in pain
but that she can cope with the help of pain medication.” The choice to make regarding this event iseither to ask her whether she wants to try reducing the pain medication or to stick to the current dose.
This is an example of an event that does link to a PM task, as in the EMR for this patient the participant
could have read that this patient’s temperature needs to be measured three times a day. In the7820

instructions of the experiment it was made clear that these type of measurements were conductedduring the medication round. After choosing one of the provided options, it is up to the participant toperform the task of taking the patient’s temperature before rolling the die again.
Using the programming language Python, a digital version of the board game was developed.
Figure 2 shows the layout of the digital cardboard. With a mouse click participants can roll the die
causing a marker to move around the board shown on a computer screen. Whenever the marker lands
on, or passes a yellow square, a pop up screen with a description of the event and the options occurs.
By clicking one of the options, the pop up screen disappears. The time correspo nding to the token’s
position on the board is always visible in the corner of the screen. If, based on an event or the time, a
PM task has to be executed, the participant has to click the button labeled ‘execute task’ to launchanother pop-up screen that allows the participant to type the task they want to conduct. The time(position of the marker on the board) of each performed task is logged and used to calculate PM
performance.

Figure 2 – Layout of the Virtual Shift board game. The red token corresponds to the virtual time,
indicated on the board with ‘Tijd’.
2.2 Study Population
Experienced nurses who are familiar with the EMR system will be asked to participate.
2.3 Sample Size Calculation
With this experiment we aim to detect a medium effect size of 0.25 for the most critical comparison
between the three sound conditions with a power of 0.8. An a-priori power calculation was performed
using G*Power software (19). The calculation was made for an ANOVA with repeated measures,within factors. The experimental design consists of one group that undergoes three measurements.
Conservative estimates were made of 0.5 for the correlation among repeated measures and anonsphericity correction of 0.5. The required sample size is 44 participants.
2.4 Sound Conditions
Three extreme conditions which can be considered realistic are modelled using Odeon 12.12
combined. The first condition represents a nurses’ station of 20 m2 with an absorptive ceiling andabsorbing elements on the wall which is modelled after an existing nurses’ station. Figure 3 shows themodel of the room and the position of the sources that were used. The receiver location (1 in Figure 3)
is located behind a desk in the room. The ambient sound environment is the result of the sound fromthe ventilation (L7 in Figure 3), the adjacent ward (which is separated from the nurses’ station by aglass wall (M6,19 and M6,21 in Figure 3)) and one person who is working on a computer but not
speaking (P5 in Figure 3). This condition is referred to as ‘dry, no speech’. The second condition issimilar to the first condition with the addition of background speech (P1 and P2 in Figure 3), ‘dry,
speech’. In the third condition, background speech is also present, and the ceiling and wall properties
are such that a more reverberant environment is created, ‘reverberant, speech’. Standard material
properties from the Odeon library, are linked to the surfaces in the model to create realistic room
acoustics (see Table 1). The acoustic properties of the ceiling, and a 1 m strip on the walls just below
the ceiling are used to create the difference between room acoustic conditions. In the reverberant
condition, these surfaces are modelled as plastered concrete while in the dry condition th ese surfaces
are covered with mineral wool.

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Figure 3 – Nurses’ station model in Odeon
The speech signals that are used in the speech scenario’s and the verbal change of shift report are to
be recorded in a semi-anechoic room using a headset. Volunteers (co-workers at the university) are
asked to read from a script that is written for each patient scenario. In both speech scenarios the
background speech script consists of a change of shift report between two colleagues an d somepersonal chatting. The source and receiver positions are marked in Figure 3. The information about thepatients that are discussed is not relevant for the participant. Since the nursing population in the
Netherlands mainly consists of females, all recorded voices are female. An ad ditional recording is
made for the change of shift report that addresses the participant.
Table 1- Material properties in Odeon model
Surface

Material code Odeon

Area

Floor

6000 – Linoleum or vinyl stuck to concrete

17.96 m2

Lower part walls

4002 – Painted plaster surface

15.6 m2

Glass walls

10003 - Double glazing, 2-3mm glass, 10 mm gap

14.3 m2

Seat covers

11005 – Empty chairs, upholstered with leather cover

4.04 m2

3062 – Plywood on battens fixed to solid backing

1.36 m2

Wooden closets

3021- 6mm wood fibre board on laths, cavity >100mm deep

10.8 m2

Desk

10- 10% absorbent

4,4 m212004- 50 mm mineral wool (40kg/m3), glued to wall

32.8m24002 – Painted plaster surface

32.8m2

Wooden panels
below seats

Upper part walls &Ceiling (dry)Upper part walls &Ceiling (reverberant)7822

2.5 Procedure
Each participant goes through the experimental procedure four times, one practice round and threeexperimental sound conditions. They are seated behind a desk in an enclosed, sound insulated office,wearing headphones. There are two computer screens on the desk, a main screen right in front of theparticipant and a second screen on the right. The main screen is connected to a keyboard. In the firstphase of the experimental task the participant sees a user interface with written instructions on themain computer screen. After reading the instructions for the first time, the participant is asked to sign
an informed consent form and click on a ‘start’ button on the user interface. In the consecutive
experimental conditions, the instructions are still part of the procedure. When the start button isclicked, the audio file corresponding to the scenario starts to play and the ward overview of the EMR
is shown on the screen. It shows all the patients who are ‘currently’ admitted to the ward, three of
which are within the participants’ care. The task of the participants is to read the patient files as if they
were starting their shift and had to care for these patients. They are instructed to think out loud while
reading the files. Intentions for actions to be performed are measured and counted by a researcher who
is sitting in the back of the room. To allow offline analysis an audio recording is made. At some point
during the reading task they are interrupted with a verbal shift transfer from a fictional colleague(embedded in the audio file with background sounds) which contains additional PM tasks to be
performed. No repetition of the PM tasks in the EMR are included in the report. Thinking aloud is not
required during the verbal change of shift report, and the assumption is made that all PM tasks received
verbally lead to forming an intention. The audio stream of the verbal shift transfer is synchronized witha video on the second computer screen. The whole process of reading and the shift transfer takes aminimum of 10 minutes and a maximum of 15 minutes, depending on the reading speed of theparticipant. When the participant has finished reading the files, a button to continue to the next part ofthe experiment can be clicked. A short break during which the participant leaves the room is held
between the first and the second part of the experiment.
In the second part of the experiment no headphones are used. The participant returns to the office
after the short break and commences the game ‘Virtual Shift’. After three circuits on the board game,the final ‘event’ that pops up informs the participants that they have finished their shift. After the gamethe participants are asked to answer a short questionnaire about the sound environment and theexperimental task. After each scenario a short break outside the room is held. It is expected that one
scenario lasts approximately 30 minutes, and the full experiment including instructions will take twohours.

3. ANALYSISThe first part of the experiment is expected to provide information on the amount of intentions thatare formed by the participant. The second part of the experiment is expected to provide information on
the amount of correctly retrieved and therefore properly encoded intentions. The maximum amount offormed PM intentions is 15, the maximum amount of retrieved PM intentions is dependent on theamount of formed intentions by each individual participant. Therefore, there is a high correlation
between the two dependent measures. To answer the main research question, whether and whichaspects of the sound environment influence the forming and encodin g of PM intentions, separate
single-factor ANOVAs are planned for both dependent measures. The independent measure is thesound condition which has three levels. Based on the results, planned comparisons will be performed
to further analyze the contribution of the two aspects of the sound environment that were included in
the experiment; the presence of background speech and the room acoustic design of the nurses’ station
in a situation with background speech. Furthermore, we aim to analyze interaction effects for the typeof PM task (time based or event based) and the presentation mode in phase one (aural or visual).

4. FINAL REMARKSThe intention of this paper was to characterize the different experimental design aspects fromdifferent disciplines that we combined in the proposed protocol while keeping the resemblance of thetask, sound conditions and the sound-task interaction as high as possible. Initially, a pilot study withexperienced nurses is planned. In this pilot study a small group of participants wi ll perform theexperiment in all three conditions followed by an interview on their experience. Furthermore, theresults of this pilot study will be used to validate the amount and difficulty of the PM tasks that can beformed based on the EMR. The content of the EMR files will be adapted to create three scenarios with7823

an equal amount of intentions to be formed.

ACKNOWLEDGEMENTS
The authors thank dr. Toros Senan for designing a digital version of the Virtual Week game.
This study is performed under the Spark II Impulse program of Eindhoven University ofTechnology.
This study is part of a project for which cofinancial contributions have been received bySaint-Gobain Ecophon. The funding source had no involvement in the study design; in the collection,
analysis and interpretation of data; in the writing of the report; and in the decision to submit the article
for publication. The authors declare no conflict of interests.

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