Possible legal opinion:

John and Ruth's situation raises potential issues of noise disturbance, breach of lease terms, and possible legal remedies. However, the specific legal analysis and outcome may depend on various factors, such as the applicable laws and regulations, the terms of their lease agreement, the building rules and policies, and the factual context of the noise level and duration.

One relevant legal framework to consider is the concept of nuisance, which generally refers to an unreasonable interference with another person's use and enjoyment of their property. Nuisance can be either private or public, depending on the scope and impact of the interference. Private nuisance involves a harm or annoyance that affects a specific individual or group of individuals, while public nuisance involves a harm or annoyance that affects the community at large. In either case, the plaintiff must prove that the defendant's conduct was both intentional and unreasonable, and that it caused a substantial and foreseeable harm.

In John and Ruth's case, John could argue that Ruth's use of her new speakers constitutes a private nuisance that interferes with his ability to study and rest. However, the reasonableness of Ruth's conduct may depend on various factors, such as the time of day, the volume and duration of the music, the type of building and insulation, and the prior notice or complaints from John or other tenants. For example, if Ruth is playing her music at a moderate level during the day or early evening, and John has not raised any objections or concerns, it may be harder for him to claim that Ruth's conduct is unreasonable or intentional. On the other hand, if Ruth is blasting her music at a high volume late at night, and John has repeatedly asked her to lower it or complained to the landlord, it may be easier for him to show that Ruth's conduct is unreasonable and intentional.

Another legal issue to consider is the lease agreement between John and Ruth and the landlord. The lease may contain provisions that address noise levels, quiet hours, and other rules and restrictions that govern the tenants' behavior. For example, the lease may require the tenants to keep the noise level below a certain decibel level, or to refrain from playing music or using loud appliances during certain hours. If Ruth is violating such provisions, John may have a contractual claim against her and/or the landlord for breach of lease. However, the enforceability and scope of such provisions may depend on various factors, such as the clarity and specificity of the language, the reasonableness of the restrictions, and the landlord's duty to enforce them.

Finally, John may have legal remedies available to him if he can prove that Ruth's conduct constitutes a legal violation or tort. For example, he may be able to sue Ruth for intentional infliction of emotional distress, if he can show that her conduct was extreme and outrageous and caused him severe emotional distress. He may also be able to seek an injunction or restraining order against Ruth, if he can show that her conduct poses a threat of irreparable harm to him. However, these remedies may be harder to obtain and enforce, and may require a higher burden of proof than a private nuisance claim.

In conclusion, John and Ruth's situation raises complex legal issues that require a careful analysis of the applicable legal standards, the lease agreement, and the factual context. While John may have some legal claims or remedies available to him, the outcome may depend on the specific facts and evidence presented. Therefore, it is advisable for John to seek legal advice and/or mediation to resolve the dispute in a fair and efficient manner.