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Authors:
Volker Schmid (1)
Klaus Focke (2)

Reading time: 
4 min

(1) Staff member of TAUBERT und RUHE GmbH, Pinneberg, and member of the DIN 8989 standard committee

(2) Executive of TAUBERT und RUHE GmbH, Pinneberg

Schallschutz Aufzugsschacht Regelung Lift report

Soundproofing rules and regulations have been revised but are still in need of improvement

Things are improving – but the road to the ultimate goal is still a bumpy one

Lift systems guarantee a freedom from barriers and a riding comfort. This is why numerous residential buildings have built-in lift systems which also improve the marketing options. Lift systems are also invariably a noise source that must be taken into account. System engineering and structural noise abatement measures must be in tune with each other. For this purpose the DIN 8989 standard „Soundproofing in buildings – Lift systems“ [1] succeeding the VDI 2566 standard „Soundproofing of lift systems with or without machine room“ Part 1 [2] and Part 2 [3] was published in August 2019. Apart from a new name the standard has a lot to offer to support manufacturers, planners and executors. The topics “Soundproofing” and “Lift systems” themselves are already very complex and also make the application of parts of the standard DIN 8989 more difficult. The following paper includes some remarks to provide a better understanding to everyone who is interested.

The soundproofing of lift systems and their appropriate shafts has been described in Directive VDI 2566 Part 1 for lift systems with machine room and has been complemented by Part 2 for lift systems without machine room. Both parts only take into account the building regulations concerning the minimum noise abatement according to standard DIN 4109, edition 1989 [4]. With the publication of standard DIN 8989 in August 2019 these two parts of the Directive VDI 2566 were withdrawn.

The standard DIN 8989 has had a relatively long time of origin. The start was made in 2008 with the revision of standard VDI 2566 – Part 1 which was published with some editorial changes in April 2011. During the revision a lot of identical regulations were found in Parts 1 and 2. In the next step an amalgamation of Parts 1 and 2 was planned in concert with a technical revision. In the last decade building owners and residents have aspired to improve the protection against noise, so that the revised Directive VDI 2566 should now take this into account as well. After some internal harmonization activities, the new Directive concept that has now come into being has been relayed by the VDI to DIN so that a new number had to be assigned.

 

Requirements

Since most of the lift systems are installed in residential buildings, the transmission of sound regularly needs to meet new demands. The decisive factor is the sound pressure level transmitted to a room of a flat that is in need of protection. No new values have been determined in DIN 8989 for the definition of requirements applying to the room in need of protection. Instead, references are made to existing demands included in other rules and regulations. Apart from the minimum requirements included in DIN 4109-1 (published last in January 2018 [5]), three sound proofing levels of Directive VDI 4100 of 2012 [6] were brought into play because they present a sensible psycho-acoustical grading tool with numbered soundproofing stages; stage I (SSt I), stage II (SSt II – improved soundproofing) and stage III (SSt III – high-grade soundproofing).

Usually the requirements to be met to protect a room are determined first, although they actually represent the end of the sound transmission from the lift to the flat. The standard DIN 8989 describes the input quantities that must exist in order to allow the soundproofing goal to be achieved. First of all the standard designates the general acoustical characteristic quantities for the lift components taken over from Directive VDI 2566 and adapted to the higher soundproofing level. It is all about the maximum permissible sound pressure level developed in front of the portal door when the door is opened and about the sound pressure level developed both inside the shaft and the cab during the lift ride. These sound pressure levels depend on the lift manufacturer and cannot be influenced by the building structure. The respective requirements are shown in table 1.

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Table 1: maximum permissible sound pressure levels as per DIN 8989

 

Demands applying to airborne soundproofing

Since the revision of standard DIN 4109-1 was published in 2018 the shaft wall has to meet an additional demand when the room in need of protection is located next to the lift shaft. An airborne soundproofing level of R’w = 57 dB has to be met. This value is usually attained for example using a 25 cm thick reinforced concrete wall. But the airborne sound transmission is uncritical because as shown in Table 1 the minimum sound pressure level inside the shaft may not exceed 75 dB(A) anyway. The resulting airborne sound emission for the specified soundproofing level amounts to approx. 20 dB(A) ± 3 dB depending on the frequency-dependent structure and the room situation. It is therefore substantially lower than the minimum soundproofing level of ≤ 30 dB(A) and as such irrelevant. In case of higher soundproofing levels the sound pressure levels to be met inside the shaft are lower so that the airborne soundproofing requirements are fulfilled.

 

Demands applying to the lift shaft wall

But in order to be able to fulfil the requirements in neighbouring flats and their workrooms, living and sleeping quarters, the transmission by the structure-borne sound is decisive. This transmission is influenced both by the lift engineering and the building structure. As already known from Directive VDI 2566, the building structure relates to the required building shell’s surface-related masses. DIN 8989 now includes new system engineering requirements referring to the maximum permissible structure-borne sound input. So-called acceleration levels are indicated which are independent of the building structure. Both the requirements to be met by the surface-related masses and by the maximum permissible structure-borne sound input increase with the rising soundproofing levels: the higher the soundproofing level the more heavy and massive structural elements and lower structure-borne sound levels are required. Therefore the surface-related mass is always designed for the most unfavourable case in the building and must be provided for the entire shaft structure. Designing shaft walls with different thicknesses has never been an option in Directive VDI 2566 and is something that the standard DIN 8989 expressly opposes.

Constraints (e.g. due to a lack of space) may sometimes exist and the planner would like to avoid the fulfilment of the DIN 8989 specifications. So planning activities will not strictly follow the standard. In this particular case the only sensible interpretation of the specifications is that merely the shaft walls to which lift components are attached will receive the specified surface-related mass. According to his own best judgement the planner can then dimension the rest of the shaft walls to which no lift components are attached in compliance with the required airborne sound specifications.

The higher surface-related mass of the shaft walls required in case of a higher or high soundproofing target according to DIN 8989 also causes a higher airborne soundproofing level. Therefore, when a directly adjoining room in need of protection requires a higher soundproofing level, there is no need for an additional higher airborne soundproofing level of the shaft wall. In some cases the characteristic values for the surface-related masses in the individual levels are identical (e.g. double-wall structures). But these are only structures which commonly are necessary for structural reasons anyway or which cannot have a less thick design.

The ground plan situation also influences the transmission of sound and therefore different situations are taken into account with respect to the demands to be met by the system engineering and building structure:

  • A: lift system within the staircase room
  • B: a room in need of protection immediately next to the lift shaft
    • single-wall or
    • double-wall design
  • C: buffer room between the lift shaft and the room in need of protection

 

Demands applying to the system engineering

Table 2 shows an excerpt of the respective demands specified in standard DIN 8989 for the directly neighbouring shaft (Situation B in the standard). The system is structured so that the difference between two levels always amounts to 3 dB. By adopting a system engineering with a lower structure-borne sound level, an improvement in the receiver room of approx. 1.5 dB is achieved from one level to another (although the actual figures of the acceleration level show a bigger gradation). A gradation in connection with the building structure contributes the other 1.5 dB.

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Table 2: the rooms in need of protection are located next to the shaft

For other neighbouring structures (such as lift shafts integrated into the stairwells and situations with buffer rooms between the lift shaft and the room in need of protection) similar demands for the acceleration levels and the required surface-related masses of the shaft walls and flanking components are made. Buffer rooms are rooms which are accessible and which can be used e.g. as storerooms, corridors, etc.  Installation shafts are not regarded as buffer rooms (provided they are located with their full face in front of the lift shaft wall) but can be assessed as annexed soundproofing shells when they show the appropriate design (resonance frequency f0 ≤ 50 Hz). The situation description „lift shaft integrated into the stairwell“ means that all around the lift shaft there is a stair system with flights and main and/or interim resting places.

The metrological verification of the acceleration level is relatively costly and difficult so that the specified solid-borne sound levels are more or less intended as planning and development specifications for the manufacturer and as a support for difficult disputes and not as a general verification during final inspection and acceptance tests. Every single manufacturer should therefore accept his responsibility to verify his products and provide correct data during award of contract negotiations.

 

Flanking components

The demands to be met by the flanking components have been reduced substantially and in DIN 8989 only constitute a bottom limit. In the former Directive VDI 2566 for example a surface-related mass of 580 kg/m² was specified for bonded-on ceilings, although this is not necessary from the soundproofing point of view. Because of general soundproofing agreements it is now typical for flanking components (ceilings, stairwell walls, etc.) inside a building to adopt additional demands from other soundproofing standards (e.g. DIN 4109, VDI 4100). As such the minimum requirements specified in the standard DIN 8989 do not determine the structure. For this purpose verification calculations have been carried out and displayed in the “Technology Block“. It has been shown that the sound radiation with common structural surface-related masses of the components connected to the shaft theoretically behave as perceived in practice.

 

Characteristic soundproofing values

The tables and characteristic values referred to so far represent the core of standard DIN 8989 and are used to plan, design and test lift systems in buildings. All these data are needed to meet the demand agreed upon for the room in need of protection. On the one hand this can be the sound pressure level of LAFmax,n ≤ 30 dB(A) specified in standard DIN 4109-1. On the other hand there can also be characteristic values and recommendations for higher soundproofing demands often to be met in case of owner-occupied flats. These are for example included in Directive VDI 4100 and amount to LAFmax,nT ≤ 30 dB(A) for the soundproofing level I (SSt I). In the other levels SSt II and SSt III the characteristic value is reduced by 3 dB, each.

With respect to the characteristic values the minimum demands and the soundproofing level I (SSt I) seem to be identical at the first glance. Attention will be paid to the different characteristic values “normalized sound pressure level LAFmax,n ” and “standardized sound pressure level LAFmax,nT” later on in this paper and a simplification will be carried out. This is where the inconspicuous letter „T“ in the index (just like many sound technology’s characteristic values) make the big difference. In standard DIN 8989 both characteristic values are indicated. Already during the first months after the publication of this standard the parallel indication of the characteristic values caused a lot of irritation. The following table 3 shows the headings of the tables 3 and 4 included in the standard DIN 8989.

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Table 3: headings of tables 3 and 4 in standard DIN 8989

The first two lines of the lists of demands 3 and 4 in standard DIN 8989 indicate that the normalized sound pressure level LAFmax,n depends on the volume. Some concrete volume limits are indicated as well. Since the physics makes no jumps, the way in which these specifications are dealt with when volume limits are slightly exceeded or underrun is critical.

When the tables 2 and 3 named here are joined in the following table 4, some contradictions become evident which need to be solved.

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Table 4: headings and demands to be met by the structural soundproofing (also table 4 in standard DIN 8989

 

Table 4 shows that with a growing volume with thicker shaft walls the soundproofing level retains the characteristic value when the normalized sound pressure level LAFmax,n is used. This could lead to the assumption that superproportionally high demands need to be met by the shaft walls and system technology when higher or very high soundproofing levels need to be achieved. Experience has shown that this is not the case when final inspection measurements of lift systems are carried out. It is also known from calculations e.g. for the verification of airborne and impact soundproofing levels that soundproofing is improved the higher the volume is because the sound energy density is reduced.

The second line of the table shows that the standardized sound pressure level LAFmax,nT is independent of the room volume. This is not accurate. Measurements and the complementary investigations (see “Technology Block“) show that similar to the airborne and impact soundproofing levels this value is more favourable when the volume of the room in need of protection increases. The standardized sound pressure level LAFmax,nT therefore is independent of the room volume – but in a positive sense.

 

Special situations

No specifications are made for rooms in which higher sound pressure levels (≤ 35 dB(A) are permissible such as offices and class rooms. This calls for the engineering skills of the planner. The same applies to lift shafts with a metal/glass design or several lifts installed in one shaft (lift groups). It may be expected from metal/glass lift shafts that the solid-borne sound transmission is smaller. But it can hardly be predicted and it will therefore only be able to plan it qualitatively in the near future. For lift groups assumptions can be based on an initial approximation – i.e. two lifts + 3 dB or 3 lifts + 5 dB and can be used for interpolation purposes in accordance with the tables of standard DIN 8989.

 

A suggestion for a revision

For a revision of the standard it would be advantageous to supplement and/or extend the demand tables. At the same time the specifications covering to the surface-related masses for the flanking components should be adapted. A relevant suggestion is made in table 5. The specifications for the maximum permissible acceleration levels are relatively new so that the practice will show if there is a further need for an adaptation. For this reason the acceleration levels were not changed in table 5 and are shown in a grey colour. For the future it would be desirable if the more practice-oriented standardized sound pressure level LAFmax,nT would be applied in standard DIN 4109, too, since this would provide a more practically relevant description. This has also been taken into account in the suggestion in table 5.

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Measuring example

When complaints are registered about the noise generated by lift systems, it is common practise that first the sound pressure level inside the room in need of protection is measured in compliance with standards DIN EN ISO 10052 [7] and DIN 4109-4 [8]. In order to improve the quality and comparability of such measurements, standard DIN 8989 includes concrete specifications for the verification by measurements. The influence of ambient noises especially during the verification of higher soundproofing demands or the necessity to measure the reverberation time inside the room might turn trivial measurements into a challenge. An exact measurement of lift rides and the accurate documentation of the technical and structural conditions often not only serve the purpose of a settlement of disputes. It might also be used to find clues allowing a possibly necessary fault diagnosis to be started. To present the sound pressure level as only one numerical value for the lift system is not very helpful. The differentiation between rides of the lift up and down the shaft, the presentation of the rides as a level/time course and the subjective description of the noises (pulses before or during the ride, grinding noises or a humming tone of a machine) are information which every expert should document when measuring the noise produced by a lift system.

Diagram 1 shows the level/time course of a continuous upward ride from the basement to the 5th floor with a 125 ms resolution. The first measurement (red) shows high pulses. The pulses up to 40 dB(A) determine the level. But the riding noises with 35 dB(A), too, are clearly perceptible because the background noise level amounts to< 20 dB(A) which can be seen from the course of the curve at the left-hand and right-hand edges of the diagram. In a second measurement (blue) the lift system was adjusted and an additional soundproofing shell was installed in the room in need of protection. By subjecting the lift system to appropriate adjustment measures the pulses were eliminated and the shell installed in front of the shaft reduced the ride noises by an additional 3 dB. The ride noises are now level-determinant at 32 dB(A). From the building legislation point of view the lift system therefore still is not OK. But the example clearly shows that both the lift technology and the building structure influence the noise level inside the room.

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Diagram 1: level/time course in the reception room during the operation of a lift system

 

Messung vorher – Measurement before
Messung nachher – Measurement after
Aufzugsfahrt aufwärts – Lift ride upwards
OG – 5th floor
KG – Basement
Schallpegel – Noise level
Messzeit – Measuring time

 

Conclusion

Standard DIN 8989 has eliminated the weak points of the former Directive VDI 2569. The specifications relating to the surface-related masses of the flanking components are more differentiated and somewhat nearer to the practise. But they need to be revised later with respect to the ceilings. An appropriate suggestion has been worked out.

The standard offers the opportunity to plan measures ensuring a higher soundproofing level. The fact that might be helpful is that there is an interaction between the system technology and the building structure since both the room in need of protection and the lift system influence the complex soundproofing subject. The present application has caused some irritation because the standard takes into account two slightly different characteristic sound engineering values stemming from different existing Directives and their demands. If one completely neglects the normalized sound pressure level LAFmax,n and exclusively applies the standardized sound pressure level LAFmax,nT, the situation is cleared up. Now if this path is followed in the revision of standard DIN 4109, things will move forward with standard DIN 8989, too.

Technology block

What is the correct characteristic soundproofing value?

For the transmission of sound by lift systems to rooms in need of protection, the surface-related masses of the shaft walls and flanking components as well as the solid-borne sound energy introduced into the shaft walls are decisive. The solid-borne sound energy is described by the acceleration level La.

The flanking components (walls and ceilings) are coupled to the shaft walls but are better protected against the sound introduction by these particular coupling points. An evaluation should also take into account the size of the particular components because bigger components proportionally radiate more sound energy. Bigger components radiate the sound energy into a bigger room volume which also has an effect on the energy density, i.e. on the audible sound pressure level.

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Fig. a): example with varying ground plan

Meanings:
Aufzug = Lift  / Schlafzimmer = Bedroom

As an example, the situation shown in Fig. a) has been investigated by calculation. The room in need of protection is a bedroom located immediately next to the lift shaft. The flanking components are assumed to meet the DIN 8989 specifications. The influence of the room volume has been taken into account by increasing the length and width of the room in steps of 1 m, each. As such, the room volume is increased in steps from 22 m³ to 225 m³. Diagram I shows the appropriate results as normalized and standardized sound pressure levels. The sound pressure levels Lp to be expected result from the theoretical approach (e.g. see Directive VDI 2081 [9]) with a sound power level LW radiated into the room, a constant reverberation time of the room of T0 = 0.5 s and a variable volume V: Lp = LW + 10 x log (T/V) + 14 dB. The normalized sound pressure level is calculated from the correction on the standard absorption surface A0 = 10 m². For the standardized sound pressure level it is in this particular case not necessary to calculate a correction because the assumed reverberation time of the reference reverberation time corresponds to T0 = 0,5 s:

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Diagram I: normalized and standardized sound pressure levels with increasing room volumes

Meanings:
Schalldruckpegel = Sound pressure level
Volumen des schutzbedürftigen Raums = Volume of the room in need of protection

 

As regards the standardized sound pressure level LAFmax,nT (blue continuous line) it becomes obvious that – as expected – it decreases the more the volume increases. In large rooms, soundproofing is better than in small rooms which is also known from considerations in connection with airborne and impact soundproofing.

 

The result of the normalized sound pressure level LAFmax,n (green dotted line) which is also specified in standard DIN 4109-1 becomes bigger the more the volume increases. As such, the 30 dB(A) value specified in DIN 4109-1 for a room with a volume of approx. 200 m³ is exceeded by more than 5 dB although the shaft wall remains unchanged. It cannot be assumed that the energy portion radiated by the flanking components is so much bigger that the sound power radiated by the shaft wall is exceeded. We must come to the conclusion that the description of the actual situation with the normalized sound pressure level is extremely inadequate. This is the reason why the normalized sound pressure level LAFmax,n, i.e. the top title line of table 3 in the main text is not very useful to characterize demands and specifications.

The result for the standardized sound pressure level LAFmax,nT (blue continuous line) shows that the sound pressure level decreases with an increasing volume. When the sound power is radiated into the room by the shaft wall only, a doubling of the room volume would result in a reduction of 3 dB. But this is not the case. The reduction amounts to a mere 1,5 dB with a double room volume. A reduction by 3 dB for this room example is only achieved with approx. 10 times the room volume. Therefore the bigger sound radiating flanking components in big room volumes affect the sound pressure level inside the room. But they have not the same strong effect as the one that could be expected according to the simplified theory.

In order to be able to determine the influence which the sound radiation of the components involved has on the sound pressure level, the interim results of the sound pressure level included in the calculation model have been assessed in percentages. Although this is quite unusual in common sound engineering examinations, it does clarify the situation.

These assessments are shown for the situations depicted in Fig. a) with the increasing room volume. Diagram II shows the appropriate results.

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Diagram II: proportional airborne sound radiation from the shaft wall and flanking components with specifications stipulated in DIN 8989

Meanings:
Anteilig abgestrahlte… = Proportionally radiated structure-borne sound energy
Raumvolumen = Room volume
Schacht = Shaft
Boden = Floor
Decke = Ceiling
lange Wand = Long wall
kurze Wand = Short wall)

Since residential buildings principally feature a floating floor, the sound radiated by this surface is irrelevant. The appropriate curve is nearly identical with the curve of the short wall’s sound radiation. The portion of the sound energy radiated by the longer flanking wall compared to the ceiling surface is also irrelevant because the ceiling surface has a bigger surface portion than the flanking wall. With the approach of the surface-related mass for the ceiling of m‘ = 300 kg/m² according to DIN 8989 (corresponding to an only 125 mm thick reinforced-concrete ceiling), the sound radiation from the ceiling is – starting from a certain volume – bigger than from the shaft wall. But this only occurs with such very thin ceilings (which even in old buildings are rather unusual). But it is evident that the shaft wall and the floor ceilings determine the sound pressure level to be expected inside the room.

Since according to diagram II the calculated proportional sound power radiated by the floor ceiling exceeds the shaft wall’s one, the surface-related mass – as is customary in building practise – should also be heavier in standard DIN 8989. With a reinforced-concrete ceiling which for example features a thickness of 180 mm, the following results as shown in diagram III is achieved:

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Diagram III: proportional airborne sound radiation from the shaft wall and flanking components  when the latter feature a customary structural design

Meanings:
Anteilig abgestrahlte… = Proportionally radiated structure-borne sound energy
Raumvolumen = Room volume
Schacht = Shaft
Boden = Floor
Decke = Ceiling
lange Wand = Long wall
kurze Wand = Short wall

 

The sound energy radiated from the shaft wall is always more dominant than the energy radiated from the floor ceiling. This corresponds to the experience made with refurbishments when the sound pressure level inside the room can generally be reduced by installing a sound-abating shell in front of the shaft wall because the flanking components are not substantially involved.

These arithmetical reflections prove that the specifications and demands of standard DIN 8989 are principally correct and practical. But a revision should include an increase of the surface-related mass of the floor ceiling e.g. to 400 kg/m². For a specification of the required soundproofing demands the room-dependent standardized sound pressure level LAFmax,nT should be used to reflect the appropriate situation in a realistic and practical manner. A specification of the normalized sound pressure level only makes sense for room volumes up to approx. 30 m³. Therefore the table of demands (table 5 in the main text) should be revised to improve its comprehensibility in connection with the surface-related masses. Other regulations and sets of rules which specify demands relating to the maximum permissible sound pressure level (e.g. in standard DIN 4109-1 with minimum demands also for sanitary installations) should also include the standardized sound pressure level as a characteristic value.

Literature:

  1. DIN 8989:2019-08, Schallschutz in Gebäuden – Aufzüge
  2. VDI 2566, Blatt 1 Schallschutz bei Aufzugsanlagen mit Triebwerksraum, Ausgabe April 2011
  3. VDI 2566, Blatt 2, Schallschutz bei Aufzugsanlagen ohne Triebwerksraum, Ausgabe Mai 2004
  4. DIN 4109:1989-11, Schallschutz im Hochbau, Anforderungen und Nachweise mit Berichtigung 1 zu DIN 4109, Ausgabe August 1992, und Änderung A1 (inzwischen zurückgezogen jedoch teilweise noch bauaufsichtlich eingeführt)
  5. DIN 4109-1:2018-01 Schallschutz im Hochbau, Mindestanforderungen
  6. VDI 4100:2012-10, Schallschutz im Hochbau, Wohnungen, Beurteilung und Vorschläge für erhöhten Schallschutz
  7. DIN EN ISO 10052:2010-10, Akustik, Messung der Luftschalldämmung und Trittschalldämmung und des Schalls von haustechnischen Anlagen in Gebäuden – Kurzverfahren
  8. DIN 4109-4:2016-07 Schallschutz im Hochbau, Bauakustische Prüfungen
  9. VDI 2081, Blatt 1: 2019-03 Geräuscherzeugung und Lärmminderung in Raumlufttechnischen Anlagen

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