Running a company like Pzizz naturally opens you to a lot of questions.
“What’s up with the name?”
“Is this… HYPNOSIS?!”
“So this is white-noise?”
“Is there science behind this?”
The science question always piques my interest, because we spend a lot of time researching and developing the methods we use in Pzizz (and there’s usually a new, interesting discovery to dive into).
Even just intuitively though, most people know sound can have great effects on our physiology. We use music to help pump us up at the gym, to focus and get work done, and even to put our children to sleep (twinkle, twinkle little star…).
But how can this intuitive knowledge be codified into ‘science’? That’s where ‘psychoacoustics’ comes in, the branch of psychology concerned with the perception of sound and its physiological effects.
There’s been a lot written about psychoacoustics already, and the field is developing quickly. There’s a good book called “The Universal Sense,” which will give you a pop-sci introduction to the literature from Brown University neuroscientist Seth Horowitz.
How does Pzizz tap into this? We have a dedicated researcher on staff whose job it is to take academic papers and translate them into actionable material our audio engineers can productionize (there’s an example of a write-up at the end of this post).
Science can point you into the general direction of what you need to be doing with the audio, but you still need really talented audio engineers and musicians to make it a reality. After all, just understanding the elements of a successful pop song doesn’t automatically make you Beyonce.
Based on all of our internal and external learnings we create sequences of sound — “Dreamscapes” — tailored to various portions of your sleep cycle.
On top of these Dreamscapes, we layer voice narrations based on clinical sleep interventions. Things like diaphragmatic and heart rate variability breathing, grounding, mindfulness meditation, guided imagery, somatic awareness, progressive muscle relaxation, autogenic training, hypnosis and more.
The methods we use are proven to treat insomnia and its causes, and are the same techniques successfully deployed in clinical studies.
How well does this all work? Well, there was a clinical trial conducted by Indiana State University about Pzizz published in the “Cognitive Technology Journal” that compared us against other solutions. We came out on top by a large, statistically significant margin; we’ve progressed very far in the intervening years, and stand today with an incredibly effective solution for great sleep at the crossroads between science, music and technology.
Harmat, L., Takács, J., & Bódizs, R. (2008). Music improves sleep quality in students. Journal of Advanced Nursing, 62(3), 327–335.
A randomized sample of 94 students (mean age 22.6) was divided into three pre-sleep stimuli exposure groups: music condition, audiobook condition, and no intervention condition (i.e. control). The inclusion criteria for participants were: poor sleep, no daytime somnolence (to rule out common sleep disorders), and no severe depressive symptoms. The exclusion criteria were: current use of hypnotics, sedatives or antidepressants; and medical diagnosis for primary sleep disorder. Participants in the music condition listened to relaxing classical music forty-five minutes before sleep-time. Statistically significant improvement in sleep quality over time was found in the music condition alone. For participants in the music condition, there was improvement over time on every relevant dimension of the the Pittsburgh Sleep Quality Index (Buysee et al. 1989), which is a still in use, self-report measure of sleep habits. Thirty of the thirty five poor sleeping music listeners became good sleepers by the end of the study according to their PSQI score. Depressive symptoms were measured at multiple time points using the Beck Depression Inventory (a common and fairly standard clinical measure). There was a statistically significant decrease in depressive symptoms over time in the music condition alone.
“Listening to music resulted in improved subjective sleep quality, shorter sleep latency, longer sleep duration, better sleep efficiency, reduced sleep disturbances and less daytime dysfunction week by week;… sleep duration showed a delayed effect since a statistically significantly longer sleep duration occurred during the second and third weeks” (Harmat, Takács, & Bódizs, 2008)
“Several studies conducted in clinical settings have suggested that sedative music may have positive effects on sleep via muscle relaxation and distraction from thoughts. Music can decrease sympathetic nervous system activity, as well as anxiety, heart rate, respiratory rate and blood pressure (Standley 1986, Good et al. 1999, Salamon et al. 2003)” (Harmat, Takács, & Bódizs, 2008)
“Students who listened to sedative classical music for 45 minutes at bedtime for 3 weeks had better global sleep quality in the second and third week than those who did not” (Harmat, Takács, & Bódizs, 2008)
“Following the 3-week intervention, 30 out of the 35 members of the music group became ‘good sleepers’” (Harmat, Takács, & Bódizs, 2008)
“music statistically significantly improved sleep quality. Sleep quality did not improve statistically significantly in the audiobook and the control group. Depressive symptoms decreased statistically significantly in the music group, but not in the group listening to audiobooks” (Harmat, Takács, & Bódizs, 2008)
“Relaxing classical music is an effective intervention in reducing sleeping problems. Nurses could use this safe, cheap and easy to learn method to treat insomnia” (Harmat, Takács, & Bódizs, 2008)
“Reinhardt (1999) investigated the influence of musical rhythm on the synchronisation and coordination of heart rate. Twenty-eight patients with chronic cancer pain in a stable phase of the disease underwent a 14-day relaxation training designed to improve the process of falling asleep. The therapy included 30-minute lullaby-like, rhythmically dominated music with gradually decreasing tempo. Reinhardt found that during the relaxation therapy trained patients showed increasing synchronisation and coordination of heart rate and musical beat. At a musical tempo between 48 and 42 beats/minute, a very stable 2:3 synchronisation was observed. Trained patients who reported the best relaxing and analgesic effects showed the highest degree of synchronisation. Bernardi et al. (2006) also confirmed that slow or meditative music can have a relaxing effect as well as an arousal effect, predominantly depending on the tempo. Sedative music with a slow tempo (42– 65 beats/minute) induces relaxation and reduces activity in the neuroendocrine system, and slow music produces a lower heart rate and blood pressure (Standley 1986). Salamon et al. (2003) confirmed that preferred classical music statistically significantly decreases systolic and diastolic blood pressure as well as anxiety levels. In addition, studies have also shown that relaxation may be induced with approximately 30 minutes of sedative music (Mockel et al. 1994)” The selection of music type was based on previous studies with sedative music (Field 1999, Johnson 2003, Lai & Good 2004). According to Gaston (1951), the tempo should be somewhere around 60–80 beats/minute.
The auditory processes implied by listening to audiobooks are similar to those implied by listening to music. Elements of speech and musical sound can be characterized by the same parameters: pitch, duration, loudness, rhythmic metrical structure, contour, articulation and timbre. A large number of researchers have tried to reveal the similarities and differences between the two domains in the brain. A recent study has provided neurophysiological data to prove the similarity between listening to music and verbal material. In this research, Broca’s area, known for its specialization to syntactical processing in language, was also activated by music perception (Koelsch et al. 2002). This suggests that the mechanisms underlying syntactical processing are shared between music and language (Patel 2003). In addition, there is a similar brain response between speech and music boundary processing, and Kno¨ sche also discovered EEG and EMG correlates for phrase boundaries in music. Neither music nor spoken language form uniform auditory streams; rather, they are structured into phrases (Kno¨ sche et al. 2005). Despite the similar cognitive and neurobiological specificity of music and language, audiobooks had no effect on sleep quality in our study. The specificity of music may concern different processing components. Some processing components appear to be genuinely specialized for music (Peretz & Hyde 2003), while other components can be involved in the processing of both music and speech (Patel et al. 1998). Several researchers have examined the therapeutic effect of music on depression (Hanser & Thompson 1994, Lai 1999, Hsu & Lai 2004) and found that music had beneficial effects on depressive symptoms. Music has been found to increase circulating endorphin levels (Mockel et al. 1994), which are associated with positive moods (Gerra et al. 1998)”
This study design provides the basic methodological requirements of solid research from a clinical perspective. These include: statistically significant results (low P-value), control and comparison groups, a randomized sample, and longitudinal data collection (over time). Additionally, this study uses common clinical measures, which increases its validity. I had some concern about the lack of an effect size measurement which means we can only know these results are most likely not by chance. We know this because there was a low P-value, which is a statistical measure, indicating low probability of these results occurring by chance if there was no relationship between the manipulated variable and the resulting changes). However the actual size of the changes is a different measure (effect size), and this missing measure is more important for determining clinical usefulness. After examining the graphed data, taking into account significant changes on the PSQI (which is divided into clinically useful increments), and considering the fact that this study was published in a major nursing journal, I would say these results are clinically relevant (i.e. practically useful). Additionally, other studies like the meta-analysis (annotations coming soon) address this issue of effect size by aggregating studies and looking at the resulting effects sizes.
“The first limitation of our study is that participants were recruited as ‘poor sleepers’ (PSQI global score >5). They were healthy people with some sleeping problems which can return into the normal range without any intervention. Secondly, we used self-report measures of sleep without verifying them objectively. Thirdly, a 3-week study period may not be sufficiently long to draw any conclusions about the sustainability of improved sleep on longer time periods. Fourthly, the stories to which participants in the audiobook group listened to may have induced different emotions, while the emotional effect of slow classical music was considerably more balanced. Fifthly, we contacted by telephone every participant once a week to assess their compliance with the protocol, but we have no further information about how frequently they listened to music or to the audiobook during the study period. Finally, a Hawthorne effect may have occurred in the study. The Hawthorne effect refers to a phenomenon which is thought to occur when people observed during a research study temporarily change their behaviour and performance”
Horowitz, S. S. (2013). The universal sense how hearing shapes the mind. New York, NY: Bloomsbury.
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Harmat, L., Takács, J., & Bódizs, R. (2008). Music improves sleep quality in students. Journal of Advanced Nursing, 62(3), 327–335.
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