CD Power, Loudness Wars, and Risk of Hearing Loss: An Honors Project

Honors Students in the BA degree program in Speech-Language-Hearing Sciences have an option of signing up for an honors contract while completing a course in their major.  This fulfills an honors degree requirement.  Students electing this option complete the regular requirements for a course as well as an additional project designed for the student by the professor who offers the course. 

 

Here is Marie's project that examined a sample of rock music CD's from 1990 to 2010.  The goals of her project were to: 1) document the trend for RMS (root-mean-square) power of CDs to learn if power increases over time (the year the CD was mastered) in her sample.  This trend has been reported elsewhere and 2)  to infer what the consequences might be for risk of hearing loss for persons who listen to CDs with different RMS levels without changing the volume control (for instance, while jogging).   

 

The text, tables and figures that follow comprise Marie's report that was submitted to fulfill her honors contract for my undergraduate hearing science course. 

 

Methods

 

Using CD recordings of popular rock music ranging from 1990 to 2010, Praat software was used to obtain average RMS power of a sample of the recording. Samples were taken from five different albums for each two-year length of time. In each CD, a released single song was used, and RMS measurements were taken using 60 second samples (from time 1:00 to 2:00).

      

 

Results

Artist	Song	Rel. Year	Avg RMS Power (dB)*
Nirvana	Smells like Teen Spirit	1991	78.46027
Nirvana	Come As You Are	1991	77.87609
Pearl Jam	Alive	1991	80.09812
Pearl Jam	Even Flow	1991	79.77917
Nirvana	Heart Shaped Box	1993	79.99189
Nirvana	All Apologies	1993	79.00152
Alice in Chains	Down in a Hole	1992	81.27465
Alice in Chains	Rooster	1992	74.93313
Alice in Chains	Grind	1995	82.3233
Alice in Chains	Heaven Beside You	1995	80.7176
Pearl Jam	Spin the Black Circle	1994	82.52034
Pearl Jam	Not for You	1994	81.56941
Matchbox 20	Push	1996	81.01531
Matchbox 20	3 AM	1996	80.34982
Creed	What's This Life For?	1997	82.12753
Creed	My Own Prison	1997	81.7389
Eve 6	Inside Out	1998	81.673
Eve 6	Leech	1998	81.26283
Blink-182	What's My Age Again?	1999	81.42304
Blink-182	All the Small Things	1999	84.00382
Godsmack	Awake	2000	83.70529
Godsmack	Greed	2000	84.43933
Creed	Higher	2000	81.97862
Creed	With Arms Wide Open	2000	80.63681
3 Doors Down	When I'm Gone	2002	82.67307
3 Doors Down	Here Without You	2002	81.51279
Red Hot Chili Peppers	By the Way	2002	82.677
Red Hot Chili Peppers	Can't Stop	2002	83.40131
Green Day	American Idiot	2004	85.26495
Green Day	Boulevard of Broken Dreams	2004	84.52495
3 Doors Down	Let Me Go	2005	83.46834
3 Doors Down	Behind Those Eyes	2005	83.43522
Red Hot Chili Peppers	Dani California	2006	84.32203
Red Hot Chili Peppers	Hump de Bump	2006	83.05219
Audioslave	Revelations	2006	84.6185
Audioslave	Original Fire	2006	85.04295
Hurt	Wars	2009	82.28482
Hurt	Pills	2009	83.17376
The Killers	Human	2008	82.96131
The Killers	Spaceman	2008	83.87393

*dB SPL values arbitrary in the table and are only useful for comparison with each other. dB SPL levels were calculated from Pa using the formula 20LOG₁₀(X/2x10^-5). Actual decibel level would depend on the volume setting of the music device.

 

 

A trend toward increasing intensity was found for the forty rock music samples. dB levels of samples from 1990 to 1993 were averaged (78.92 dB) and subtracted from the average of 2005 to 2009 samples (83.83 dB), and a 4.9 dB SPL change overall was found.

 

Discussion of Potential Hearing Risk

 

The National Institute for Occupational Safety and Health (NIOSH) sets a standard for hearing safety in noise in an effort to prevent occupational hearing loss. NIOSH specifies that the maximum permissible level of noise is 85 dB SPL. At 85 dB, workers are allowed a 100% noise dose, which is defined as “noise exposure expressed as a percentage of the allowable daily [work day] exposure.” So, a 100% noise dose at maximum permissible level means hearing 85 dB noise for 8 hours. NIOSH considers this to be the safety cutoff for noise. To determine noise dose for sounds louder or softer than 85 dB, NIOSH uses a 3 dB exchange rate, sometimes referred to as a doubling rate. NIOSH specifies that for every 3 dB increase in intensity, noise dose is considered to double. This means that for every 3 dB increase, safe listening time is halved. An 85 dB noise can be listened to for 8 hours without damaging hearing, but an 88 dB noise can only be listened to for 4 hours. http://www.cdc.gov/niosh/docs/96-110/appA.html

 

What does this mean for music intensity and hearing damage? Zalewski and Baur (2008) measured Preferred Loudness Levels (PLL) of men and women who used portabe mp3 devices. They found that when listening to music devices in noise (similar to the experience of wearing earbuds in an outdoor or public setting) men set their devices at 91.94 dB and women at 84.53 dB SPL. Applying NIOSH standards, men can only safely listen to their music for less than 2 hours, and women safely around 8. If listeners set their PLL for a song released in 1990 during shuffled play, music released later, which may be 4.9 dB louder, can damage their hearing in much less time.

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