Sound sensitivity in dogs: protecting emotional welfare and the human–pet bond

An awareness of, and readiness to respond to, novel or sudden sounds is a basic survival strategy for any animal that possesses an auditory system. As a consequence, sensitivity to sound deployed in such circumstances should be considered a natural state. However, for many companion animals sensitivity to sound extends not only to noises that are excessive or unexpected, but also to ‘everyday’ domestic and urban sounds; such clinically recognisable sound sensitivities encompass fear, anxiety and phobia-based responses to a range of sound-related stimuli, such as volume, pitch and suddenness (Sherman, 2008).

As a result of social restrictions put in place during the pandemic, dogs may also respond negatively to sounds that would previously have been ignored as part of the daily ‘soundscape’ within the animal's environment. These situations can create specific sensitivities that result in a reluctance to enter, or inability to relax in, specific environments where such sounds have previously been encountered. As this response will be associated with emotions of anxiety and fear, affected animals experience stress and engage behaviours intended to limit their exposure to potential threat. In addition, the concurrent unconscious non-associative and conditioning will have long-term effects on the animal, creating a need to avoid situations previously associated with, or predicting exposure to sound events. Following this, the result of future exposure to such sensitised sound events, or their predictive social or environmental clues, can become an emotional welfare problem, as when natural coping mechanisms (such as escape and avoidance) are frustrated, the result of the dog's attempts to avoid exposure to stimuli may become a potential danger to humans and other animals in their proximity.

Companion animals' hearing

With minor variations for breeds with floppy or folded ears, the basic structure and functioning of the majority of dogs' ears is very similar. Designed to capture and funnel sound down the ear canal, the ears form an effective ‘early warning’ system for a range of changing circumstances, providing time for social species such as dogs to seek out social companions and for any species to seek a place of safety (RSPCA, 2019).

Dogs can hear sounds that are up to four times quieter than humans can detect (Fay, 1988) and of much higher frequencies up to 50kHz, while the average human ear is unable to detect sounds of more than 20kHz (Hubrecht et al, 2017). Hence, dogs can detect sounds such as those produced by rodents and bats, as well as the sound of equipment used to detect burglars and deter pests and birds – stimuli using the frequencies that Grigg et al (2021) found dogs to be most sound sensitive to. Dogs' sense of hearing is linked to sense of balance and enables it to monitor its environment, detecting potential danger (such as social stimuli and motor vehicles), locating potential prey and in responding to the vocalisations of humans and conspecifics (Strain, 2011). However, the dog's capacity for fine discrimination between sounds and the accurate pinpointing of its source, through the use of their very mobile pinna and the ability to distinguish arrival sounds between the left and right ear, seems to have primarily developed to optimise predation upon small rodents (Bradshaw and Rooney, 2017).

It is clear that nature has created a highly effective system for dealing with a world where sounds are sporadic and relevant; however, the sensitivity of a companion animal's auditory sense is not always ideal for a domestic or urban environment that constantly bombards the system with sounds that, though novel or presented in an unusual manner, are largely inconsequential to the dog's safety.

Avoiding sound sensitivity

Bearing in mind the purpose of the companion animals' auditory system, it is easy to understand why so many animals will attempt to avoid sudden or unusual sounds and why this is one of the most common sources of anxiety or fear-related behaviours in dogs (Fagundes et al, 2018; Grigg, 2021). However, although some animals are predisposed to sound sensitivities as a result of genetic, epigenetic and pre-birth factors, if appropriate early intervention occurs within the breeding environment, helping young puppies to become habituated (Table 1) to a wide range of domestic and urban sounds, then the likelihood of future sensitisation (Table 1) to sounds can be avoided (Blackwell et al, 2005; Hubrecht, 2017).

Between the age of 3 and 8 weeks (with individual variation that may result in an earlier termination), puppies are in a predominantly para-sympathetic state that enhances their capacity for habituation – a form of non-associative learning that enables an animal to learn not to respond to a stimulus. As a consequence, if during this period of emotional development breeders expose young animals to gradually increasing levels of stimulation from a wide range of sounds associated with the domestic environments in a variety of formats and varying environments, a substantial reduction in the percentage of sound sensitive companion animals can be achieved (Blackwell et al, 2013; Levine et al, 2008).

Pre-dispositions to sensitivity to the sound of social and environmental activity

Following from a puppy's 8th week, the primary response to novel or sudden encounters increasingly involves the sympathetic nervous system, meaning that from this time onwards there is an increasing likelihood of sensitisation to stimuli and by the time that a puppy is approximately 14 weeks of age, unless the young animal is genetically predisposed to a relaxed response, sensitisation becomes the primary response to novel encounters, particularly if they are sudden, extreme or accompanied by other traumatic events.

Several studies have indicated that young dogs go through a period of heightened sensitivity to novel social and environmental encounters immediately following the end of the ‘socialisation period’ and up to approximately 20 weeks of age (Serpell et al, 2017), while others identify two further developmental periods of heightened social and environmental sensitivity that have profound effects upon the emotional health and behaviour of the dog: sexual maturity (the timing of which is dependent on breed and individual differences), and social maturity (between 18 and 36 months of age). In addition to these periods of sensitivity to their surroundings, dogs may also lose previous learned competencies following periods of stress (such as during illness) or periods of isolation from exposure to stimuli – a process termed ‘dishabituation’ (Table 1; Mills, 2013).

It is likely that a further period of predisposition to environmental sensitivity will occur concurrent to cognitive and sensory decline in the senior dog (Denenberg, 2021). Consequently, although dogs can suddenly alter their responses to sudden or loud noises at any stage in their life, there are four when the previously ‘sound competent’ dog will be particularly vulnerable to developing sound sensitivity.

The role of physical welfare in sensitising dogs to sound

A range of medical conditions have been associated with the apparent onset of sound sensitivity, including cognitive dysfunction (Landsberg et al, 2011) and other, less specific conditions, such as gastrointestinal problems and thyroid problems (Fagundes et al, 2018). However, a study by Fagundes et al (2018) demonstrated a strong link between the development of sound sensitivities in older dogs and concurrent medical problems, principally those involving pain and, in particular, pain resulting from orthopaedic problems. In addition, increased sound sensitivities arising as a result of, or concurrent to, pain-related conditions were more likely to:

• Generalise to a wider range of sounds
• Generalise to sensitivity of other types of stimuli in a wider range of environments.

Specific sensitivites and generalisation

It is clear that dogs are innately sound sensitive, but those described as clinically sound sensitive have an exaggerated response to sound stimuli that can negatively impact welfare (de Souza et al, 2018). The condition is both widespread (Storengen and Lingaas, 2015) and, as it results in a generalised reduction in an individual's capacity to cope (thereby sensitising the animal to other social and environmental stimuli), and/or the reduced capacity of the animal already struggling to tolerate a situation of depleted welfare being sensitised to changes in its ‘normal’ sound-scape, the condition is frequently associated with other behavioural problems (Overall, 2001; Wormald et al, 2017).

An accurate figure for incidence has proven difficult to ascertain as it is largely dependent upon owner reporting (de Souza et al, 2018), requiring owners to not only be capable of recognising common signs of sound-related distress (Box 1) but also to be able to recognise that some of the signs that dogs display may be misinterpreted as positive (such as seeking attention, tail wagging used to gain owner attention, vocalising and running back and forth from a window from which stimuli such as fireworks can be observed). In addition, some researchers have identified that many of the signs that observant owners would normally expect to see in a distressed dog (such as lip-licking or yawning) are actually less frequently seen in cases of sound-sensitivity, further reducing the accuracy of owner reporting (de Souza et al, 2018). Behavioural intervention in sound sensitivity cases is further impeded by the many owners who consider the behaviour of their sound sensitive pets to be a source of amusement (Grigg et al, 2021).

It has also been suggested that besides the behavioural reaction, sound stimuli may cause marked autonomic activation (de Souza et al, 2018), and that the subsequent cortisol release can ultimately lead to reduced immunity and increased risk of conditions such as hypertension, heart disease, fatigue and insomnia (McEwen, 2007; Teixeira et al, 2015).

Box 1.Common sources and signs of sound senstivityStimuli commonly associated with sound sensivity:

• Thunder
• Fireworks
• Gunfire
• Bird scarers
• Emergency alarms.

Sound sensitivity is also increasingly resulting from more ‘everyday’ situations such as:

• Passing traffic or pedestrians
• Children playing
• Overhead aircrafts
• Visitors arriving
• Building work.

Behaviours frequently recognised as being associated with sound sensitivty:

• Active responses: alertness, scanning, searching for the source of sound, being startled, restlessness, aimless or repetetive pacing, bolting, barking, whining, searchibng for caregiver, self-mutilation, destructiveness, digging, running, circling, climbing, jumping
• Passive fear or anxiety responses: trembling, shaking, hiding, panting, arched posture, salivation, ears back, crouching or cowering, freezing against a wall or door, tail between legs, tensing, yawning, lip-licking, lifting forelegs.

Dreschel (2010) found that dogs with non-social fear and separation anxiety experienced significantly increased severity and frequency of skin disorders, and dogs with a fear of strangers had a significantly shorter lifespan; this resulted in Bowen et al (2012) suggesting that, as the worst affected noise-sensitive dogs will eliminate or vomit during noise events, it is probable these animals are at a high risk of stress-related health problems.

The most commonly described sound sensitivities

Most frequently reported to veterinary teams are sensitivities to the sound of fireworks, thunder and gunshots (BSAVA, 2022). Less frequently reported by owners are the very similar sounds associated with situations such as the back-firing of cars and the bird scarers used in rural areas following the seeding of fields. Because they rely so heavily upon owner perceptions, figures for the incidence rate of sound sensitivity may be under-reported, but still frequently quoted are the results of Blackwell et al's (2005) study, which showed that 49% of dogs show fear in response to at least one type of sound. It is likely that only those dogs showing extremely obvious signs of distress or behaviours, that can be considered inconvenient to owners, are likely to be presented to a veterinary surgeon, a figure of only 29% of the 49% identified in the study were presented at a veterinary practice (the nature of the support received potentially being limited to ‘over the counter’ discussions with support staff). However, the failure of an animal's sound-related behaviour to inconvenience an owner sufficiently to seek veterinary intervention is no indication of the level of distress suffered by the animal (BSAVA, 2022). Blackwell et al (2005) were unable to look at the severity of the fear problems reported, so it is not known what proportion of dogs were so badly affected that the problem had an impact on their health or quality of life. Further studies have led to the development of an online sound sensitivity questionnaire, characterising a number of aspects of noise fear in dogs (Calvo et al, 2011; Bowen et al, 2012). The studies supported the same figure for dogs displaying a fear of loud noises, but also classified about a third of those fearful dogs as severely affected, responding to fireworks, thunder or gunshot noises so distant they were almost inaudible to owners. These dogs showed high levels of distress during noise events and, following an incident, they took an extended period of time to recover, some remaining obviously distressed for up to 24 hours after the event, representing a considerable impairment to quality of life.

When sound sensitivity becomes a phobia

As the emotions of anxiety and fear and their associated neural networks are intended to create adaptive behaviours aimed at improving the animal's chance of survival (Levine, 2009), the animal naturally enhances this survival mechanism by learning to avoid situations that have a strong predictive potential regarding likely exposure to problem stimului (Overall, 2002). Subsequently, sound-related fears that go untreated in companion animals extend to an ever-widening array of stimuli, and sounds similar to the initiating sound begin to elicit the same anxiety or fear-related behaviours, such as with thunder, gunshots or fireworks. The array of stimuli eliciting fear-related behaviours may expand to include the ‘whoosh’ of traffic on a wet road, party poppers or clapping – sounds that are similar to those of the ascending firework and eventual explosion. This ‘generalising’ effect may also ‘chain’ outwards to include the sound and sight of physical or social stimuli that were present at the time of exposure to a sound event (clapping, cheering, sudden noises, loud or angry voices, crying or screaming children or dropped objects, plus environmental stimuli that are present at the time of exposure), all of which may begin to initiate similarly intense signs of fear. Eventually, completely innocuous events that had previously been a pleasurable part of the animal's routine (such as the sight of a harness or lead that represents being taken outdoors for a walk on a dark night) may become predictive of exposure to a ‘sound event’, thereby becoming increasingly daunting for the animal (Bowen and Heath, 2005). Such ‘chaining’ processes are commonly associated with sound sensitivities (Figure 1). Once the sound sensitivity results in an animal no longer being able to fully engage with its normal environment, it may be considered that the fear has developed into a phobia (Bowen and Heath, 2005).

Are loud, occasional sounds the extent of the problem?

Typically, veterinary practices see a flurry of owner interest regarding their sound sensitive pets around the seasons when the use of fireworks can be expected (Bowen et al, 2012), but this presentation is often too late for anything other than ‘situational’ medical support to be put into place, which is unlikely to address the wider welfare needs of the sound sensitive dog who requires behavioural support and possibly long-term accompanying psychotropic medication. In addition, it fails to recognise the potential for sensitisation of the animal to everyday sounds inside the home and their implications for predisposed phobias, or to the sensitivity to everyday, outdoor sound events, which may ultimately result in phobias to activities within the home and a reduced willingness to engage in outdoor activity.

There are now tools available for the veterinary team and owners to assess the severity of a dog's problem with sounds and to help to initiate discussions with the veterinary team regarding both behavioural and psychopharmaceutical support (see Useful resources).

In addition to the four life-stages associated with an increased sensitivity to the dog's environment, there are two further initiators of sound sensitivity that can occur at any time in an animal's life: dishabituation and exposure to trauma (Baker et al, 2020). Dishabituation commonly occurs when an animal is undergoing a period of increased stress (such as that associated with ongoing pain or exposure to stimuli after a period of isolation) and subsequent, chronically raised cortisol levels; the frequent or ongoing stress results in a loss of previous habituation and hence increasing sensitisation (Mills et al, 2013). Exposure to any excessive or sudden loud sound that results in a startle response may create a traumatic, learned response.

The ‘covid-effect’

At the start of the COVID-19 related social lockdown periods in spring 2020, the author was requested to consider the potential ill-effects of ‘lockdown’ on the emotional health of the UK's dogs (Hargrave, 2021). One of the issues flagged up in this article was the potential for dogs experiencing reduced exposure to both social and environmental stimuli to experience dishabituation and a subsequent loss of previous social and environmental competencies. In addition, there was the serious risk that the many puppies that joined homes during the lockdown periods would fail to gain opportunities to experience habituation to normal levels of social and environmental experiences, leaving them vulnerable to sensitisation following a return to more normal levels of exposure.

Dogs have an innate requirement for a sense of coping (Mills et al, 2013) and as a result of their need to retain secure access to essential resources, many dogs show signs of preparatory arousal on hearing or seeing stimuli approach or enter their home; but in late March 2020, the environment outside our homes suddenly became a much quieter place. The normal background soundscape to which many dogs had habituated, including the sound of passing cars, motorbikes, the rush-hour slamming of household and car doors, the chatter and calls of children on their way to school or as they waited for school buses, suddenly stopped, as did the sound of visitors approaching and entering homes.

As a profession, clinical behaviourists expected to experience a considerable volume of post-lockdown cases related to dogs, both puppies taken into homes during lockdown periods and dogs that were already established within homes, whose social competencies were not sufficiently plastic to cope with post-lockdown social encounters. However, in addition to the expected social problems, and predisposing such problems, are the considerable number of dogs that are being presented to clinical animal behaviourists for social problems but that are also displaying new, or substantially increased sensitivity to everyday sounds. Although some of these dogs may have previously shown some territorial sensitivity and initiated barking in response to the sound of people approaching their homes, the level of barking, preparatory arousal and occasional aggression now being initiated in response to the sound of ‘outdoor’ stimuli appears to represent a marked increase in territorial activity. As dogs' primary alarm system for approaching danger and threat is its auditory system, these dogs are effectively displaying a considerable level of sound sensitivity to a wide range of everyday and in many cases, previously habituated sounds.

This effect represents a considerable welfare problem for affected dogs, as they are continuously exposed to the distress of sound sensitivity while within their homes and, when owners try to enhance their dogs' welfare with opportunities for outdoor exercise, the problem worsens as outdoor exposure intensifies the level of auditory exposure. In addition, for many environmentally naive or recently sensitised dogs, once the stimulus is ‘in sight’, the visual component to the stimulus merely intensifies the experience of anxiety, fear or frustration.

The previous focus of the alleviation of sound sensitivities had concentrated on occasional adverse events that, with planning, could be avoided or at least managed (regarding levels of exposure and use of short-term anxiolysis), but there is now a sound-related emotional health problem that many dogs find both continuous and impossible to avoid. Such chronic exposure to stressors is not just deleterious to the affected dog's emotional and physical health (de Souza, 2017), but the constant experience of threat may create a requirement for a physical response (such as the repetitive turning of the head during road-side exercise of a dog that is exposed to traffic approaching from behind), which is both mentally and physically exhausting. The cumulative effect of the emotions of anxiety, fear and/or frustration will further predispose affected animals to a loss of coping and a reduced tolerance of subsequent challenges that are met within their environment.

An affected dog's inability to produce a behavioural response that will alleviate such a chronic threat will inevitably result not only in the activation of anxiety/fear neural networks, but their ‘failure’ to resolve the problem will also initiate the emotion of frustration. For some dogs, this will have the effect of creating ‘learned helplessness’, resulting in behavioural inhibition (Mills et al, 2013). Other dogs will respond differently to their emotional distress, such as initiating avoidance strategies (including refusal to leave the home or behaviours intended to repel the advance of visitors who approach the home). However, all affected dogs will experience a depletion in emotional health and a reduction in the ability to cope, with subsequent lessening of the capacity to deal with further social and environmental stressors.

The resulting failure or reduction in coping will pre-dispose affected dogs to anti-social behaviours intended to maintain social distancing. However, the associated neurochemical release during such sound sensitivity events is incompatible with enabling the dog to learn positive associations with its environs, compounding the animals' experience of distress with each successive exposure. Dogs that find themselves unable to cope and subsequently experience failure to escape or avoid their situation may redirect their frustration towards other social stimuli within their environment, often in the format of aggression (Mills et al, 2013), thereby endangering family members, visitors to the home, strangers met during exercise, and other animals encountered both in and outside the home.

Noise has been shown to result in epigenetic effects (Leso et al, 2020), causing changes in gene transcription, meaning that traumatic, anxiety or fear-inducing events may affect the behaviour of future offspring of affected dogs. Therfore, the increased incidence of more generalised sensitivity to domestic and urban noises in our canine companions may continue to affect the emotional health of future generations of dogs.

Support for sound sensitive dogs

Once a sound sensitivity has been detected, the primary aim should be to protect the affected animal from exposure to the eliciting stimuli (Baker, et al 2020), thereby enhancing the animal's welfare and reducing the likelihood that the animal will enter an emotional state that is incompatible with learning about coping and safety.

In some instances, such as during a firework season, this may be the only option open to owners who have been unable to gain advice regarding the use of suitable short-term or situational anxiolysis. For those owners who have 3 months or more notice to a sound exposure, behaviour therapy involving desensitisation and counter-conditioning (which can lead to up to a 70% reduction in sound sensitivity within 8 weeks) is advisable (Bowen, 2015). However, if a dog is so sensitive to a sound that it is impossible for an owner to identify a starting point for desensitisation, or if the dog's environment makes it impossible for the dog to be protected from the sound, then long-term psychotropic support, concurrent to any behavioural therapy, is likely to be required. As sound sensitivity is a considerable welfare problem and, as long-term psychotropic support takes several weeks to become effective, or if owners have no method of protecting their dog from a specific sound event, then drugs that provide short term anxiolysis can be considered essential to their welfare (Baker et al, 2020; Warnes, 2021). However, it should be noted that emergency sound sensitivity management should not be used as a permanent management tool in this long-term welfare problem.

Ideally, owners would identify their dog's sound sensitivity before it becomes a severe problem, as the chances of resolution decrease with time – with only 4% of affected dogs showing a spontaneous resolution (Blackwell et al, 2005). Owners may find it helpful if veterinary staff guide them to the online sound sensitivity tool (see Useful resources) to assess the severity of a dog's sound sensitivity and the most appropriate starting point for treatment. Veterinary staff and clinical behaviourists will also benefit from investigating Lincoln University's sound sensitivity scale. However, for individual sounds to which a dog has recently been exposed (such as the cries of a new baby in a household), Lincoln's canine anxiety scale can also be very useful.

Pharmacological support for sound sensitive dogs

Many sound sensitive dogs are too aware of soundscape or ‘phobic stimuli’ to be able to attain a sufficient level of relaxation to be able to embark upon new learning through behaviour therapy alone, and such dogs require the support of veterinary medicines. As the author is not a veterinary surgeon, it is not their place to offer advice on this subject, although there is an increasing wealth of support available for veterinary staff, either in the form of books specific to the subject (Crowell-Davis et al, 2019; Denenberg, 2021), articles (Baker et al, 2020; Warnes, 2021) or, alternatively, in the form of ‘free to access' webinars, such as those on the veterinary area of the Fellowship of Animal Behaviour Clinicians website. Animals receiving psychopharmaceutical support will still require behaviour modification to improve long-term coping and a register of clinical animal behaviourists and veterinary behaviourists can be found on the websites of Fellowship of Animal Behaviour Clinicians and the Animal Behaviour and Training Council.

Conclusions

A fear or phobia of loud noises has, for some time, been the most common and best understood behavioural problem affecting the UK's companion dog population. However, it is this author's opinion that, particularly since the COVID-19-related social lockdown periods, a considerable proportion of the UK's dog population has become sensitised to the sound of an increasing range of everyday sounds associated with the outdoor and urban environment, leaving many dogs with a reduced concept of coping and safety, which both reduces their overall welfare and pre-disposes affected dogs to other social and environmental sensitivities and behaviour problems.

There is now a range of tools, some free of charge, that veterinary staff can access to help them to assess the level of sound-related distress experienced by their canine patients, enabling more targeted treatment, which when used alongside appropriate behavioural support, can provide relief from this invasive and distressing welfare problem. For many dogs, sound sensitivity is no longer a short-term annual problem, but an everyday encounter that blights their lives. It is time that queries about sound sensitivity became part of the conversation within every routine veterinary consultation.

Useful resources

• CEVA sound sensitivity questionnaire: https://blog.adaptil.com/uk/does-my-dog-have-noise-anxiety
• Dogs Trust sound therapy for pets: https://www.dogstrust.org.uk/help-advice/dog-behaviour-health/sound-therapy-for-pets
• Fellowship of Animal Behaviour Clinicians: https://fabclinicians.org/find-a-behaviourist/
• RSPCA ‘bang out of order’ campaign: https://www.rspca.org.uk/documents/1494939/0/Bang+out+of+order+-+fireworks+frighten+animals+%28PDF+706KB%29.pdf/ebcfb65c-40f4-58a0-88d2-0896845a3127?t=1571669349793
• Animal Behaviour and Training Council: https://abtc.org.uk/practitioners/
• Lincoln University's sound sensitivity scale: https://ipstore.lincoln.ac.uk/product/the-lincoln-sound-sensitivity-scale-for-dogs-lsss
• Lincoln University's canine anxiety scale: https://ipstore.lincoln.ac.uk/product/the-lincoln-canine-anxiety-scale-lcas
• John Bowen (thewebinarvet.com) – noise-related anxiety in dogs and how to manage it: https://players.brightcove.net/1455209554001/4b151501-5a1d-4344-a13e-6f5f4ca46dcb_default/index.html?videoId=5653677414001

KEY POINTS

• The incidence of sound-sensitivity within the domestic pet population would appear to be underestimated.
• The emotional welfare problem associated with the well recognised, occasional, loud sound events continues to be under managed and under treated.
• Many owners continue to fail to notice fearfulness in their dogs in response to household and everyday noises.
• Better education is required for dog owners to accurately interpret canine body language, to both safeguard dogs' welfare and minimise the distress associated with sound-sensitivities.
• The veterinary profession is best placed to initiate discussions with owners regarding their dogs' social and environmental competencies.